[toc]

写在文章开头

近期有打算写一些关于redis源码系列的文章，为了深入了解redis的设计，笔者索性在WSL上搭建了一套可调试的redis环境，遂以此文整理一下个人的配置过程。

2025.8.2考虑到mac os的用户，笔者基于此文补充一下关于mac os下通过vscode调试reids的步骤。

我是 SharkChili，Java 开发者，Java Guide开源项目维护者。欢迎关注我的公众号：写代码的SharkChili，也欢迎您了解我的开源项目 mini-redis：https://github.com/shark-ctrl/mini-redis。

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详解WSL下调试redis配置步骤

前置WSL环境准备

微软提供了一套Windows环境下的Linux子系统，通过这套系统我们可以直接基于Linux子系统调试C语言代码，因为本文着重是演示如何配置redis调试环境，所以对于WSL就不做过多介绍，有需要的读者可移步官方文档完成WSL环境基本配置和安装:

适用于 Linux 的 Windows 子系统文档 (opens new window)

然后就是准备C语言环境了，首先更新一下软件包并安装c/c++开发要用到编译、开发、调试工具。

sudo apt update
sudo apt install g++ gdb make ninja-build rsync zip

然后就是WSL与vscode关联的配置:

开始通过适用于 Linux 的 Windows 子系统使用 Visual Studio Code (opens new window)

Visual Studio Code安装C语言相关插件

因为要调试C语言代码环境，所以这里完成vscode安装之后，我们需要安装如下几个类型拓展插件:

1. C/C++相关插件。
2. CMake相关插件。

这里笔者也给出安装插件的截图：

拉取代码并完成基础配置和编译

完成C语言基本环境配置后，我们就可以拉取对应版本的redis源码到Linux子系统上了，因为笔者主要是了解redis和核心设计，所以直接选择3.0.0版本，对应的拉取指令如下：

git clone -b 3.0.0 https://github.com/redis/redis.git

完成代码拉取之后，我们需要通过vim编辑src/Makefile文件，如下所示，将OPTIMIZATION?改为-O0，将REDIS_LD设置为$(QUIET_LINK)$(CC) $(FINAL_LDFLAGS) $(OPTIMIZATION)，从而避免一些代码的一些优化导致代码无法进行准确定位和调试，对应修改如下所示：

# OPTIMIZATION?=-O2
OPTIMIZATION?=-O0
# REDIS_LD=$(QUIET_LINK)$(CC) $(FINAL_LDFLAGS)
REDIS_LD=$(QUIET_LINK)$(CC) $(FINAL_LDFLAGS) $(OPTIMIZATION)

最后就是编译，笔者通过make执行编译执行时输出了如下错误：

jemalloc/jemalloc.h: No such file or directory。

按照redis官方仓库给出的提示，redis默认情况下采用jemalloc 进行编译和链接，所以对于上述问题我们可以直接采用指令make MALLOC=libc进行编译：

---------

Selecting a non-default memory allocator when building Redis is done by setting
the `MALLOC` environment variable. Redis is compiled and linked against libc
malloc by default, with the exception of jemalloc being the default on Linux
systems. This default was picked because jemalloc has proven to have fewer
fragmentation problems than libc malloc.

To force compiling against libc malloc, use:

    % make MALLOC=libc

To compile against jemalloc on Mac OS X systems, use:

    % make MALLOC=jemalloc

Verbose build

自此我们源码所有的准备工作都完成了。

基于VSCode调试源码

通过WSL下键入code . 打开vscode，通过open folder进入redis的根目录，定位到redis.c键入F5，运行就会有提示要求配置tasks.json(构建说明)和launch.json(调试器设置)两个文件配置，tasks.json配置如下，只需指定编译的shell指令make即可：

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "shell",
            "type": "shell",
            "command": "/usr/bin/make"
        }
    ]
}

然后我们再给出lauch.json，配置都是固定的：

1. 指明调试器类型为cppdbg。
2. 设置可执行文件路径program为redis-server。
3. 参数args设置为redis配置文件redis.conf。
4. 调试工具MIMode为gdb。

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "gcc build and debug active file",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/src/redis-server",
            "args": [
                "redis.conf"
            ],
            "stopAtEntry": true,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "preLaunchTask": "shell"
        }
    ]
}

启动测试

完成这些基础配置，此时我们就可以通过VScode调试redis源码了，如下所示，指定调试模式基于我们的配置并启动：

自此我们就可以愉快的从redis入口源码开始了解redis的设计与实现了：

详解mac os下基于vscode调试redis配置步骤

分支选择

针对mac os，笔者查阅众多资料最终选择了redis 3.2.12版本，对应的拉取指令为：

git clone -b 3.2.12 https://github.com/redis/redis.git

redis源码基本配置(make all编译未报错可跳过)

因为mac os是类unix的操作系统，所以在调试上无需经过wsl，所以笔者仅下载安装了如下几个调试c语言的插件

完成基本插件下载安装后，就可以开始配置mac os平台下对于redis源码的配置了，默认情况下笔者编译redis时先抛出了如下错误，即熟mac os不支持大文件函数：

'fstat64'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]

但是现在的macos已经支持了，所以我们需要在配置上调整一下，避免这个编译报错，首先定位到config.c定位到如下配置：

#if defined(__APPLE__) && !defined(MAC_OS_X_VERSION_10_6)
#define redis_fstat fstat64
#define redis_stat stat64
#else
#define redis_fstat fstat
#define redis_stat stat
#endif

然后在这些配置上方追加一行告知当前mac os可以使用fstat的这个处理大文件的宏：

#define MAC_OS_X_VERSION_10_6

随后再次执行编译抛出如下错误：

/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/mach/arm/_structs.h:141:13: note: '__sp' declared here
        __uint64_t __sp;    /* Stack pointer x31 */

参考GitHub上某位外国友人的的答案，通过修改debug.c配置，对应的他也将这个修改达成补丁patch，我们只需将其补丁下载并存到redis的根目录下执行git apply 03-REIDS-APPLE-SILCON-CHIP.patch即可，对应的下载地址为：https://github.com/RedisOptimal/redis-cluster-support-mget/blob/c0ad6cb108d29f795f87f7abb0de63650b185499/03-REIDS-APPLE-SILCON-CHIP.patch

考虑到读者的时间成本，笔者这里索性将修改后的debug.c源码贴出来：

#include "server.h"
#include "sha1.h"   /* SHA1 is used for DEBUG DIGEST */
#include "crc64.h"

#include <arpa/inet.h>
#include <signal.h>

#ifdef HAVE_BACKTRACE
#include <execinfo.h>
#include <ucontext.h>
#include <fcntl.h>
#include "bio.h"
#include <unistd.h>
#include <dlfcn.h>
#endif /* HAVE_BACKTRACE */

#ifdef __CYGWIN__
#ifndef SA_ONSTACK
#define SA_ONSTACK 0x08000000
#endif
#endif

/* ================================= Debugging ============================== */

/* Compute the sha1 of string at 's' with 'len' bytes long.
 * The SHA1 is then xored against the string pointed by digest.
 * Since xor is commutative, this operation is used in order to
 * "add" digests relative to unordered elements.
 *
 * So digest(a,b,c,d) will be the same of digest(b,a,c,d) */
void xorDigest(unsigned char *digest, void *ptr, size_t len) {
    SHA1_CTX ctx;
    unsigned char hash[20], *s = ptr;
    int j;

    SHA1Init(&ctx);
    SHA1Update(&ctx,s,len);
    SHA1Final(hash,&ctx);

    for (j = 0; j < 20; j++)
        digest[j] ^= hash[j];
}

void xorObjectDigest(unsigned char *digest, robj *o) {
    o = getDecodedObject(o);
    xorDigest(digest,o->ptr,sdslen(o->ptr));
    decrRefCount(o);
}

/* This function instead of just computing the SHA1 and xoring it
 * against digest, also perform the digest of "digest" itself and
 * replace the old value with the new one.
 *
 * So the final digest will be:
 *
 * digest = SHA1(digest xor SHA1(data))
 *
 * This function is used every time we want to preserve the order so
 * that digest(a,b,c,d) will be different than digest(b,c,d,a)
 *
 * Also note that mixdigest("foo") followed by mixdigest("bar")
 * will lead to a different digest compared to "fo", "obar".
 */
void mixDigest(unsigned char *digest, void *ptr, size_t len) {
    SHA1_CTX ctx;
    char *s = ptr;

    xorDigest(digest,s,len);
    SHA1Init(&ctx);
    SHA1Update(&ctx,digest,20);
    SHA1Final(digest,&ctx);
}

void mixObjectDigest(unsigned char *digest, robj *o) {
    o = getDecodedObject(o);
    mixDigest(digest,o->ptr,sdslen(o->ptr));
    decrRefCount(o);
}

/* Compute the dataset digest. Since keys, sets elements, hashes elements
 * are not ordered, we use a trick: every aggregate digest is the xor
 * of the digests of their elements. This way the order will not change
 * the result. For list instead we use a feedback entering the output digest
 * as input in order to ensure that a different ordered list will result in
 * a different digest. */
void computeDatasetDigest(unsigned char *final) {
    unsigned char digest[20];
    char buf[128];
    dictIterator *di = NULL;
    dictEntry *de;
    int j;
    uint32_t aux;

    memset(final,0,20); /* Start with a clean result */

    for (j = 0; j < server.dbnum; j++) {
        redisDb *db = server.db+j;

        if (dictSize(db->dict) == 0) continue;
        di = dictGetSafeIterator(db->dict);

        /* hash the DB id, so the same dataset moved in a different
         * DB will lead to a different digest */
        aux = htonl(j);
        mixDigest(final,&aux,sizeof(aux));

        /* Iterate this DB writing every entry */
        while((de = dictNext(di)) != NULL) {
            sds key;
            robj *keyobj, *o;
            long long expiretime;

            memset(digest,0,20); /* This key-val digest */
            key = dictGetKey(de);
            keyobj = createStringObject(key,sdslen(key));

            mixDigest(digest,key,sdslen(key));

            o = dictGetVal(de);

            aux = htonl(o->type);
            mixDigest(digest,&aux,sizeof(aux));
            expiretime = getExpire(db,keyobj);

            /* Save the key and associated value */
            if (o->type == OBJ_STRING) {
                mixObjectDigest(digest,o);
            } else if (o->type == OBJ_LIST) {
                listTypeIterator *li = listTypeInitIterator(o,0,LIST_TAIL);
                listTypeEntry entry;
                while(listTypeNext(li,&entry)) {
                    robj *eleobj = listTypeGet(&entry);
                    mixObjectDigest(digest,eleobj);
                    decrRefCount(eleobj);
                }
                listTypeReleaseIterator(li);
            } else if (o->type == OBJ_SET) {
                setTypeIterator *si = setTypeInitIterator(o);
                robj *ele;
                while((ele = setTypeNextObject(si)) != NULL) {
                    xorObjectDigest(digest,ele);
                    decrRefCount(ele);
                }
                setTypeReleaseIterator(si);
            } else if (o->type == OBJ_ZSET) {
                unsigned char eledigest[20];

                if (o->encoding == OBJ_ENCODING_ZIPLIST) {
                    unsigned char *zl = o->ptr;
                    unsigned char *eptr, *sptr;
                    unsigned char *vstr;
                    unsigned int vlen;
                    long long vll;
                    double score;

                    eptr = ziplistIndex(zl,0);
                    serverAssert(eptr != NULL);
                    sptr = ziplistNext(zl,eptr);
                    serverAssert(sptr != NULL);

                    while (eptr != NULL) {
                        serverAssert(ziplistGet(eptr,&vstr,&vlen,&vll));
                        score = zzlGetScore(sptr);

                        memset(eledigest,0,20);
                        if (vstr != NULL) {
                            mixDigest(eledigest,vstr,vlen);
                        } else {
                            ll2string(buf,sizeof(buf),vll);
                            mixDigest(eledigest,buf,strlen(buf));
                        }

                        snprintf(buf,sizeof(buf),"%.17g",score);
                        mixDigest(eledigest,buf,strlen(buf));
                        xorDigest(digest,eledigest,20);
                        zzlNext(zl,&eptr,&sptr);
                    }
                } else if (o->encoding == OBJ_ENCODING_SKIPLIST) {
                    zset *zs = o->ptr;
                    dictIterator *di = dictGetIterator(zs->dict);
                    dictEntry *de;

                    while((de = dictNext(di)) != NULL) {
                        robj *eleobj = dictGetKey(de);
                        double *score = dictGetVal(de);

                        snprintf(buf,sizeof(buf),"%.17g",*score);
                        memset(eledigest,0,20);
                        mixObjectDigest(eledigest,eleobj);
                        mixDigest(eledigest,buf,strlen(buf));
                        xorDigest(digest,eledigest,20);
                    }
                    dictReleaseIterator(di);
                } else {
                    serverPanic("Unknown sorted set encoding");
                }
            } else if (o->type == OBJ_HASH) {
                hashTypeIterator *hi;
                robj *obj;

                hi = hashTypeInitIterator(o);
                while (hashTypeNext(hi) != C_ERR) {
                    unsigned char eledigest[20];

                    memset(eledigest,0,20);
                    obj = hashTypeCurrentObject(hi,OBJ_HASH_KEY);
                    mixObjectDigest(eledigest,obj);
                    decrRefCount(obj);
                    obj = hashTypeCurrentObject(hi,OBJ_HASH_VALUE);
                    mixObjectDigest(eledigest,obj);
                    decrRefCount(obj);
                    xorDigest(digest,eledigest,20);
                }
                hashTypeReleaseIterator(hi);
            } else {
                serverPanic("Unknown object type");
            }
            /* If the key has an expire, add it to the mix */
            if (expiretime != -1) xorDigest(digest,"!!expire!!",10);
            /* We can finally xor the key-val digest to the final digest */
            xorDigest(final,digest,20);
            decrRefCount(keyobj);
        }
        dictReleaseIterator(di);
    }
}

#if defined(USE_JEMALLOC)
void inputCatSds(void *result, const char *str) {
    /* result is actually a (sds *), so re-cast it here */
    sds *info = (sds *)result;
    *info = sdscat(*info, str);
}
#endif

void debugCommand(client *c) {
    if (c->argc == 1) {
        addReplyError(c,"You must specify a subcommand for DEBUG. Try DEBUG HELP for info.");
        return;
    }

    if (!strcasecmp(c->argv[1]->ptr,"help")) {
        void *blenp = addDeferredMultiBulkLength(c);
        int blen = 0;
        blen++; addReplyStatus(c,
        "DEBUG <subcommand> arg arg ... arg. Subcommands:");
        blen++; addReplyStatus(c,
        "segfault -- Crash the server with sigsegv.");
        blen++; addReplyStatus(c,
        "restart  -- Graceful restart: save config, db, restart.");
        blen++; addReplyStatus(c,
        "crash-and-recovery <milliseconds> -- Hard crash and restart after <milliseconds> delay.");
        blen++; addReplyStatus(c,
        "assert   -- Crash by assertion failed.");
        blen++; addReplyStatus(c,
        "reload   -- Save the RDB on disk and reload it back in memory.");
        blen++; addReplyStatus(c,
        "loadaof  -- Flush the AOF buffers on disk and reload the AOF in memory.");
        blen++; addReplyStatus(c,
        "object <key> -- Show low level info about key and associated value.");
        blen++; addReplyStatus(c,
        "sdslen <key> -- Show low level SDS string info representing key and value.");
        blen++; addReplyStatus(c,
        "populate <count> [prefix] -- Create <count> string keys named key:<num>. If a prefix is specified is used instead of the 'key' prefix.");
        blen++; addReplyStatus(c,
        "digest   -- Outputs an hex signature representing the current DB content.");
        blen++; addReplyStatus(c,
        "sleep <seconds> -- Stop the server for <seconds>. Decimals allowed.");
        blen++; addReplyStatus(c,
        "set-active-expire (0|1) -- Setting it to 0 disables expiring keys in background when they are not accessed (otherwise the Redis behavior). Setting it to 1 reenables back the default.");
        blen++; addReplyStatus(c,
        "lua-always-replicate-commands (0|1) -- Setting it to 1 makes Lua replication defaulting to replicating single commands, without the script having to enable effects replication.");
        blen++; addReplyStatus(c,
        "error <string> -- Return a Redis protocol error with <string> as message. Useful for clients unit tests to simulate Redis errors.");
        blen++; addReplyStatus(c,
        "structsize -- Return the size of different Redis core C structures.");
        blen++; addReplyStatus(c,
        "htstats <dbid> -- Return hash table statistics of the specified Redis database.");
        blen++; addReplyStatus(c,
        "jemalloc info  -- Show internal jemalloc statistics.");
        blen++; addReplyStatus(c,
        "jemalloc purge -- Force jemalloc to release unused memory.");
        setDeferredMultiBulkLength(c,blenp,blen);
    } else if (!strcasecmp(c->argv[1]->ptr,"segfault")) {
        *((char*)-1) = 'x';
    } else if (!strcasecmp(c->argv[1]->ptr,"restart") ||
               !strcasecmp(c->argv[1]->ptr,"crash-and-recover"))
    {
        long long delay = 0;
        if (c->argc >= 3) {
            if (getLongLongFromObjectOrReply(c, c->argv[2], &delay, NULL)
                != C_OK) return;
            if (delay < 0) delay = 0;
        }
        int flags = !strcasecmp(c->argv[1]->ptr,"restart") ?
            (RESTART_SERVER_GRACEFULLY|RESTART_SERVER_CONFIG_REWRITE) :
             RESTART_SERVER_NONE;
        restartServer(flags,delay);
        addReplyError(c,"failed to restart the server. Check server logs.");
    } else if (!strcasecmp(c->argv[1]->ptr,"oom")) {
        void *ptr = zmalloc(ULONG_MAX); /* Should trigger an out of memory. */
        zfree(ptr);
        addReply(c,shared.ok);
    } else if (!strcasecmp(c->argv[1]->ptr,"assert")) {
        if (c->argc >= 3) c->argv[2] = tryObjectEncoding(c->argv[2]);
        serverAssertWithInfo(c,c->argv[0],1 == 2);
    } else if (!strcasecmp(c->argv[1]->ptr,"reload")) {
        if (rdbSave(server.rdb_filename) != C_OK) {
            addReply(c,shared.err);
            return;
        }
        emptyDb(NULL);
        if (rdbLoad(server.rdb_filename) != C_OK) {
            addReplyError(c,"Error trying to load the RDB dump");
            return;
        }
        serverLog(LL_WARNING,"DB reloaded by DEBUG RELOAD");
        addReply(c,shared.ok);
    } else if (!strcasecmp(c->argv[1]->ptr,"loadaof")) {
        if (server.aof_state == AOF_ON) flushAppendOnlyFile(1);
        emptyDb(NULL);
        if (loadAppendOnlyFile(server.aof_filename) != C_OK) {
            addReply(c,shared.err);
            return;
        }
        server.dirty = 0; /* Prevent AOF / replication */
        serverLog(LL_WARNING,"Append Only File loaded by DEBUG LOADAOF");
        addReply(c,shared.ok);
    } else if (!strcasecmp(c->argv[1]->ptr,"object") && c->argc == 3) {
        dictEntry *de;
        robj *val;
        char *strenc;

        if ((de = dictFind(c->db->dict,c->argv[2]->ptr)) == NULL) {
            addReply(c,shared.nokeyerr);
            return;
        }
        val = dictGetVal(de);
        strenc = strEncoding(val->encoding);

        char extra[128] = {0};
        if (val->encoding == OBJ_ENCODING_QUICKLIST) {
            char *nextra = extra;
            int remaining = sizeof(extra);
            quicklist *ql = val->ptr;
            /* Add number of quicklist nodes */
            int used = snprintf(nextra, remaining, " ql_nodes:%u", ql->len);
            nextra += used;
            remaining -= used;
            /* Add average quicklist fill factor */
            double avg = (double)ql->count/ql->len;
            used = snprintf(nextra, remaining, " ql_avg_node:%.2f", avg);
            nextra += used;
            remaining -= used;
            /* Add quicklist fill level / max ziplist size */
            used = snprintf(nextra, remaining, " ql_ziplist_max:%d", ql->fill);
            nextra += used;
            remaining -= used;
            /* Add isCompressed? */
            int compressed = ql->compress != 0;
            used = snprintf(nextra, remaining, " ql_compressed:%d", compressed);
            nextra += used;
            remaining -= used;
            /* Add total uncompressed size */
            unsigned long sz = 0;
            for (quicklistNode *node = ql->head; node; node = node->next) {
                sz += node->sz;
            }
            used = snprintf(nextra, remaining, " ql_uncompressed_size:%lu", sz);
            nextra += used;
            remaining -= used;
        }

        addReplyStatusFormat(c,
            "Value at:%p refcount:%d "
            "encoding:%s serializedlength:%zu "
            "lru:%d lru_seconds_idle:%llu%s",
            (void*)val, val->refcount,
            strenc, rdbSavedObjectLen(val),
            val->lru, estimateObjectIdleTime(val)/1000, extra);
    } else if (!strcasecmp(c->argv[1]->ptr,"sdslen") && c->argc == 3) {
        dictEntry *de;
        robj *val;
        sds key;

        if ((de = dictFind(c->db->dict,c->argv[2]->ptr)) == NULL) {
            addReply(c,shared.nokeyerr);
            return;
        }
        val = dictGetVal(de);
        key = dictGetKey(de);

        if (val->type != OBJ_STRING || !sdsEncodedObject(val)) {
            addReplyError(c,"Not an sds encoded string.");
        } else {
            addReplyStatusFormat(c,
                "key_sds_len:%lld, key_sds_avail:%lld, "
                "val_sds_len:%lld, val_sds_avail:%lld",
                (long long) sdslen(key),
                (long long) sdsavail(key),
                (long long) sdslen(val->ptr),
                (long long) sdsavail(val->ptr));
        }
    } else if (!strcasecmp(c->argv[1]->ptr,"populate") &&
               (c->argc == 3 || c->argc == 4)) {
        long keys, j;
        robj *key, *val;
        char buf[128];

        if (getLongFromObjectOrReply(c, c->argv[2], &keys, NULL) != C_OK)
            return;
        dictExpand(c->db->dict,keys);
        for (j = 0; j < keys; j++) {
            snprintf(buf,sizeof(buf),"%s:%lu",
                (c->argc == 3) ? "key" : (char*)c->argv[3]->ptr, j);
            key = createStringObject(buf,strlen(buf));
            if (lookupKeyWrite(c->db,key) != NULL) {
                decrRefCount(key);
                continue;
            }
            snprintf(buf,sizeof(buf),"value:%lu",j);
            val = createStringObject(buf,strlen(buf));
            dbAdd(c->db,key,val);
            signalModifiedKey(c->db,key);
            decrRefCount(key);
        }
        addReply(c,shared.ok);
    } else if (!strcasecmp(c->argv[1]->ptr,"digest") && c->argc == 2) {
        unsigned char digest[20];
        sds d = sdsempty();
        int j;

        computeDatasetDigest(digest);
        for (j = 0; j < 20; j++)
            d = sdscatprintf(d, "%02x",digest[j]);
        addReplyStatus(c,d);
        sdsfree(d);
    } else if (!strcasecmp(c->argv[1]->ptr,"sleep") && c->argc == 3) {
        double dtime = strtod(c->argv[2]->ptr,NULL);
        long long utime = dtime*1000000;
        struct timespec tv;

        tv.tv_sec = utime / 1000000;
        tv.tv_nsec = (utime % 1000000) * 1000;
        nanosleep(&tv, NULL);
        addReply(c,shared.ok);
    } else if (!strcasecmp(c->argv[1]->ptr,"set-active-expire") &&
               c->argc == 3)
    {
        server.active_expire_enabled = atoi(c->argv[2]->ptr);
        addReply(c,shared.ok);
    } else if (!strcasecmp(c->argv[1]->ptr,"lua-always-replicate-commands") &&
               c->argc == 3)
    {
        server.lua_always_replicate_commands = atoi(c->argv[2]->ptr);
        addReply(c,shared.ok);
    } else if (!strcasecmp(c->argv[1]->ptr,"error") && c->argc == 3) {
        sds errstr = sdsnewlen("-",1);

        errstr = sdscatsds(errstr,c->argv[2]->ptr);
        errstr = sdsmapchars(errstr,"\n\r","  ",2); /* no newlines in errors. */
        errstr = sdscatlen(errstr,"\r\n",2);
        addReplySds(c,errstr);
    } else if (!strcasecmp(c->argv[1]->ptr,"structsize") && c->argc == 2) {
        sds sizes = sdsempty();
        sizes = sdscatprintf(sizes,"bits:%d ",(sizeof(void*) == 8)?64:32);
        sizes = sdscatprintf(sizes,"robj:%d ",(int)sizeof(robj));
        sizes = sdscatprintf(sizes,"dictentry:%d ",(int)sizeof(dictEntry));
        sizes = sdscatprintf(sizes,"sdshdr5:%d ",(int)sizeof(struct sdshdr5));
        sizes = sdscatprintf(sizes,"sdshdr8:%d ",(int)sizeof(struct sdshdr8));
        sizes = sdscatprintf(sizes,"sdshdr16:%d ",(int)sizeof(struct sdshdr16));
        sizes = sdscatprintf(sizes,"sdshdr32:%d ",(int)sizeof(struct sdshdr32));
        sizes = sdscatprintf(sizes,"sdshdr64:%d ",(int)sizeof(struct sdshdr64));
        addReplyBulkSds(c,sizes);
    } else if (!strcasecmp(c->argv[1]->ptr,"htstats") && c->argc == 3) {
        long dbid;
        sds stats = sdsempty();
        char buf[4096];

        if (getLongFromObjectOrReply(c, c->argv[2], &dbid, NULL) != C_OK)
            return;
        if (dbid < 0 || dbid >= server.dbnum) {
            addReplyError(c,"Out of range database");
            return;
        }

        stats = sdscatprintf(stats,"[Dictionary HT]\n");
        dictGetStats(buf,sizeof(buf),server.db[dbid].dict);
        stats = sdscat(stats,buf);

        stats = sdscatprintf(stats,"[Expires HT]\n");
        dictGetStats(buf,sizeof(buf),server.db[dbid].expires);
        stats = sdscat(stats,buf);

        addReplyBulkSds(c,stats);
    } else if (!strcasecmp(c->argv[1]->ptr,"jemalloc") && c->argc == 3) {
#if defined(USE_JEMALLOC)
        if (!strcasecmp(c->argv[2]->ptr, "info")) {
            sds info = sdsempty();
            je_malloc_stats_print(inputCatSds, &info, NULL);
            addReplyBulkSds(c, info);
        } else if (!strcasecmp(c->argv[2]->ptr, "purge")) {
            char tmp[32];
            unsigned narenas = 0;
            size_t sz = sizeof(unsigned);
            if (!je_mallctl("arenas.narenas", &narenas, &sz, NULL, 0)) {
                sprintf(tmp, "arena.%d.purge", narenas);
                if (!je_mallctl(tmp, NULL, 0, NULL, 0)) {
                    addReply(c, shared.ok);
                    return;
                }
            }
            addReplyError(c, "Error purging dirty pages");
        } else {
            addReplyErrorFormat(c, "Valid jemalloc debug fields: info, purge");
        }
#else
        addReplyErrorFormat(c, "jemalloc support not available");
#endif
    } else {
        addReplyErrorFormat(c, "Unknown DEBUG subcommand or wrong number of arguments for '%s'",
            (char*)c->argv[1]->ptr);
    }
}

/* =========================== Crash handling  ============================== */

void _serverAssert(char *estr, char *file, int line) {
    bugReportStart();
    serverLog(LL_WARNING,"=== ASSERTION FAILED ===");
    serverLog(LL_WARNING,"==> %s:%d '%s' is not true",file,line,estr);
#ifdef HAVE_BACKTRACE
    server.assert_failed = estr;
    server.assert_file = file;
    server.assert_line = line;
    serverLog(LL_WARNING,"(forcing SIGSEGV to print the bug report.)");
#endif
    *((char*)-1) = 'x';
}

void _serverAssertPrintClientInfo(client *c) {
    int j;

    bugReportStart();
    serverLog(LL_WARNING,"=== ASSERTION FAILED CLIENT CONTEXT ===");
    serverLog(LL_WARNING,"client->flags = %d", c->flags);
    serverLog(LL_WARNING,"client->fd = %d", c->fd);
    serverLog(LL_WARNING,"client->argc = %d", c->argc);
    for (j=0; j < c->argc; j++) {
        char buf[128];
        char *arg;

        if (c->argv[j]->type == OBJ_STRING && sdsEncodedObject(c->argv[j])) {
            arg = (char*) c->argv[j]->ptr;
        } else {
            snprintf(buf,sizeof(buf),"Object type: %u, encoding: %u",
                c->argv[j]->type, c->argv[j]->encoding);
            arg = buf;
        }
        serverLog(LL_WARNING,"client->argv[%d] = \"%s\" (refcount: %d)",
            j, arg, c->argv[j]->refcount);
    }
}

void serverLogObjectDebugInfo(robj *o) {
    serverLog(LL_WARNING,"Object type: %d", o->type);
    serverLog(LL_WARNING,"Object encoding: %d", o->encoding);
    serverLog(LL_WARNING,"Object refcount: %d", o->refcount);
    if (o->type == OBJ_STRING && sdsEncodedObject(o)) {
        serverLog(LL_WARNING,"Object raw string len: %zu", sdslen(o->ptr));
        if (sdslen(o->ptr) < 4096) {
            sds repr = sdscatrepr(sdsempty(),o->ptr,sdslen(o->ptr));
            serverLog(LL_WARNING,"Object raw string content: %s", repr);
            sdsfree(repr);
        }
    } else if (o->type == OBJ_LIST) {
        serverLog(LL_WARNING,"List length: %d", (int) listTypeLength(o));
    } else if (o->type == OBJ_SET) {
        serverLog(LL_WARNING,"Set size: %d", (int) setTypeSize(o));
    } else if (o->type == OBJ_HASH) {
        serverLog(LL_WARNING,"Hash size: %d", (int) hashTypeLength(o));
    } else if (o->type == OBJ_ZSET) {
        serverLog(LL_WARNING,"Sorted set size: %d", (int) zsetLength(o));
        if (o->encoding == OBJ_ENCODING_SKIPLIST)
            serverLog(LL_WARNING,"Skiplist level: %d", (int) ((zset*)o->ptr)->zsl->level);
    }
}

void _serverAssertPrintObject(robj *o) {
    bugReportStart();
    serverLog(LL_WARNING,"=== ASSERTION FAILED OBJECT CONTEXT ===");
    serverLogObjectDebugInfo(o);
}

void _serverAssertWithInfo(client *c, robj *o, char *estr, char *file, int line) {
    if (c) _serverAssertPrintClientInfo(c);
    if (o) _serverAssertPrintObject(o);
    _serverAssert(estr,file,line);
}

void _serverPanic(char *msg, char *file, int line) {
    bugReportStart();
    serverLog(LL_WARNING,"------------------------------------------------");
    serverLog(LL_WARNING,"!!! Software Failure. Press left mouse button to continue");
    serverLog(LL_WARNING,"Guru Meditation: %s #%s:%d",msg,file,line);
#ifdef HAVE_BACKTRACE
    serverLog(LL_WARNING,"(forcing SIGSEGV in order to print the stack trace)");
#endif
    serverLog(LL_WARNING,"------------------------------------------------");
    *((char*)-1) = 'x';
}

void bugReportStart(void) {
    if (server.bug_report_start == 0) {
        serverLogRaw(LL_WARNING|LL_RAW,
        "\n\n=== REDIS BUG REPORT START: Cut & paste starting from here ===\n");
        server.bug_report_start = 1;
    }
}

#ifdef HAVE_BACKTRACE
static void *getMcontextEip(ucontext_t *uc) {
#if defined(__APPLE__) && !defined(MAC_OS_X_VERSION_10_6)
    /* OSX < 10.6 */
    #if defined(__x86_64__)
    return (void*) uc->uc_mcontext->__ss.__rip;
    #elif defined(__i386__)
    return (void*) uc->uc_mcontext->__ss.__eip;
    #else
    return (void*) uc->uc_mcontext->__ss.__srr0;
    #endif
#elif defined(__APPLE__) && defined(MAC_OS_X_VERSION_10_6)
    /* OSX >= 10.6 */
    #if defined(_STRUCT_X86_THREAD_STATE64) && !defined(__i386__)
    return (void*) uc->uc_mcontext->__ss.__rip;
    #elif defined(__i386__)
    return (void*) uc->uc_mcontext->__ss.__eip;
    #else
    /* OSX ARM64 APPLE SILCON CHIP */
    return (void*) arm_thread_state64_get_pc(uc->uc_mcontext->__ss);
    #endif
#elif defined(__linux__)
    /* Linux */
    #if defined(__i386__)
    return (void*) uc->uc_mcontext.gregs[14]; /* Linux 32 */
    #elif defined(__X86_64__) || defined(__x86_64__)
    return (void*) uc->uc_mcontext.gregs[16]; /* Linux 64 */
    #elif defined(__ia64__) /* Linux IA64 */
    return (void*) uc->uc_mcontext.sc_ip;
    #elif defined(__arm__) /* Linux ARM */
    return (void*) uc->uc_mcontext.arm_pc;
    #endif
#else
    return NULL;
#endif
}

void logStackContent(void **sp) {
    int i;
    for (i = 15; i >= 0; i--) {
        unsigned long addr = (unsigned long) sp+i;
        unsigned long val = (unsigned long) sp[i];

        if (sizeof(long) == 4)
            serverLog(LL_WARNING, "(%08lx) -> %08lx", addr, val);
        else
            serverLog(LL_WARNING, "(%016lx) -> %016lx", addr, val);
    }
}

void logRegisters(ucontext_t *uc) {
    serverLog(LL_WARNING|LL_RAW, "\n------ REGISTERS ------\n");

/* OSX */
#if defined(__APPLE__) && defined(MAC_OS_X_VERSION_10_6)
  /* OSX AMD64 */
    #if defined(_STRUCT_X86_THREAD_STATE64) && !defined(__i386__)
    serverLog(LL_WARNING,
    "\n"
    "RAX:%016lx RBX:%016lx\nRCX:%016lx RDX:%016lx\n"
    "RDI:%016lx RSI:%016lx\nRBP:%016lx RSP:%016lx\n"
    "R8 :%016lx R9 :%016lx\nR10:%016lx R11:%016lx\n"
    "R12:%016lx R13:%016lx\nR14:%016lx R15:%016lx\n"
    "RIP:%016lx EFL:%016lx\nCS :%016lx FS:%016lx  GS:%016lx",
        (unsigned long) uc->uc_mcontext->__ss.__rax,
        (unsigned long) uc->uc_mcontext->__ss.__rbx,
        (unsigned long) uc->uc_mcontext->__ss.__rcx,
        (unsigned long) uc->uc_mcontext->__ss.__rdx,
        (unsigned long) uc->uc_mcontext->__ss.__rdi,
        (unsigned long) uc->uc_mcontext->__ss.__rsi,
        (unsigned long) uc->uc_mcontext->__ss.__rbp,
        (unsigned long) uc->uc_mcontext->__ss.__rsp,
        (unsigned long) uc->uc_mcontext->__ss.__r8,
        (unsigned long) uc->uc_mcontext->__ss.__r9,
        (unsigned long) uc->uc_mcontext->__ss.__r10,
        (unsigned long) uc->uc_mcontext->__ss.__r11,
        (unsigned long) uc->uc_mcontext->__ss.__r12,
        (unsigned long) uc->uc_mcontext->__ss.__r13,
        (unsigned long) uc->uc_mcontext->__ss.__r14,
        (unsigned long) uc->uc_mcontext->__ss.__r15,
        (unsigned long) uc->uc_mcontext->__ss.__rip,
        (unsigned long) uc->uc_mcontext->__ss.__rflags,
        (unsigned long) uc->uc_mcontext->__ss.__cs,
        (unsigned long) uc->uc_mcontext->__ss.__fs,
        (unsigned long) uc->uc_mcontext->__ss.__gs
    );
    logStackContent((void**)uc->uc_mcontext->__ss.__rsp);
    #elif defined(__i386__)
    /* OSX x86 */
    serverLog(LL_WARNING,
    "\n"
    "EAX:%08lx EBX:%08lx ECX:%08lx EDX:%08lx\n"
    "EDI:%08lx ESI:%08lx EBP:%08lx ESP:%08lx\n"
    "SS:%08lx  EFL:%08lx EIP:%08lx CS :%08lx\n"
    "DS:%08lx  ES:%08lx  FS :%08lx GS :%08lx",
        (unsigned long) uc->uc_mcontext->__ss.__eax,
        (unsigned long) uc->uc_mcontext->__ss.__ebx,
        (unsigned long) uc->uc_mcontext->__ss.__ecx,
        (unsigned long) uc->uc_mcontext->__ss.__edx,
        (unsigned long) uc->uc_mcontext->__ss.__edi,
        (unsigned long) uc->uc_mcontext->__ss.__esi,
        (unsigned long) uc->uc_mcontext->__ss.__ebp,
        (unsigned long) uc->uc_mcontext->__ss.__esp,
        (unsigned long) uc->uc_mcontext->__ss.__ss,
        (unsigned long) uc->uc_mcontext->__ss.__eflags,
        (unsigned long) uc->uc_mcontext->__ss.__eip,
        (unsigned long) uc->uc_mcontext->__ss.__cs,
        (unsigned long) uc->uc_mcontext->__ss.__ds,
        (unsigned long) uc->uc_mcontext->__ss.__es,
        (unsigned long) uc->uc_mcontext->__ss.__fs,
        (unsigned long) uc->uc_mcontext->__ss.__gs
    );
    logStackContent((void**)uc->uc_mcontext->__ss.__esp);
    #else
    /* OSX ARM64 APPLE SILCON CHIP */
    serverLog(LL_WARNING,
    "\n"
    "x0:%016lx x1:%016lx x2:%016lx x3:%016lx\n"
    "x4:%016lx x5:%016lx x6:%016lx x7:%016lx\n"
    "x8:%016lx x9:%016lx x10:%016lx x11:%016lx\n"
    "x12:%016lx x13:%016lx x14:%016lx x15:%016lx\n"
    "x16:%016lx x17:%016lx x18:%016lx x19:%016lx\n"
    "x20:%016lx x21:%016lx x22:%016lx x23:%016lx\n"
    "x24:%016lx x25:%016lx x26:%016lx x27:%016lx\n"
    "x28:%016lx fp:%016lx lr:%016lx\n"
    "sp:%016lx pc:%016lx cpsr:%08lx\n",
        (unsigned long) uc->uc_mcontext->__ss.__x[0],
        (unsigned long) uc->uc_mcontext->__ss.__x[1],
        (unsigned long) uc->uc_mcontext->__ss.__x[2],
        (unsigned long) uc->uc_mcontext->__ss.__x[3],
        (unsigned long) uc->uc_mcontext->__ss.__x[4],
        (unsigned long) uc->uc_mcontext->__ss.__x[5],
        (unsigned long) uc->uc_mcontext->__ss.__x[6],
        (unsigned long) uc->uc_mcontext->__ss.__x[7],
        (unsigned long) uc->uc_mcontext->__ss.__x[8],
        (unsigned long) uc->uc_mcontext->__ss.__x[9],
        (unsigned long) uc->uc_mcontext->__ss.__x[10],
        (unsigned long) uc->uc_mcontext->__ss.__x[11],
        (unsigned long) uc->uc_mcontext->__ss.__x[12],
        (unsigned long) uc->uc_mcontext->__ss.__x[13],
        (unsigned long) uc->uc_mcontext->__ss.__x[14],
        (unsigned long) uc->uc_mcontext->__ss.__x[15],
        (unsigned long) uc->uc_mcontext->__ss.__x[16],
        (unsigned long) uc->uc_mcontext->__ss.__x[17],
        (unsigned long) uc->uc_mcontext->__ss.__x[18],
        (unsigned long) uc->uc_mcontext->__ss.__x[19],
        (unsigned long) uc->uc_mcontext->__ss.__x[20],
        (unsigned long) uc->uc_mcontext->__ss.__x[21],
        (unsigned long) uc->uc_mcontext->__ss.__x[22],
        (unsigned long) uc->uc_mcontext->__ss.__x[23],
        (unsigned long) uc->uc_mcontext->__ss.__x[24],
        (unsigned long) uc->uc_mcontext->__ss.__x[25],
        (unsigned long) uc->uc_mcontext->__ss.__x[26],
        (unsigned long) uc->uc_mcontext->__ss.__x[27],
        (unsigned long) uc->uc_mcontext->__ss.__x[28],
        (unsigned long) arm_thread_state64_get_fp(uc->uc_mcontext->__ss),
        (unsigned long) arm_thread_state64_get_lr(uc->uc_mcontext->__ss),
        (unsigned long) arm_thread_state64_get_sp(uc->uc_mcontext->__ss),
        (unsigned long) arm_thread_state64_get_pc(uc->uc_mcontext->__ss),
        (unsigned long) uc->uc_mcontext->__ss.__cpsr
    );
    logStackContent((void**) arm_thread_state64_get_sp(uc->uc_mcontext->__ss));
    #endif
/* Linux */
#elif defined(__linux__)
    /* Linux x86 */
    #if defined(__i386__)
    serverLog(LL_WARNING,
    "\n"
    "EAX:%08lx EBX:%08lx ECX:%08lx EDX:%08lx\n"
    "EDI:%08lx ESI:%08lx EBP:%08lx ESP:%08lx\n"
    "SS :%08lx EFL:%08lx EIP:%08lx CS:%08lx\n"
    "DS :%08lx ES :%08lx FS :%08lx GS:%08lx",
        (unsigned long) uc->uc_mcontext.gregs[11],
        (unsigned long) uc->uc_mcontext.gregs[8],
        (unsigned long) uc->uc_mcontext.gregs[10],
        (unsigned long) uc->uc_mcontext.gregs[9],
        (unsigned long) uc->uc_mcontext.gregs[4],
        (unsigned long) uc->uc_mcontext.gregs[5],
        (unsigned long) uc->uc_mcontext.gregs[6],
        (unsigned long) uc->uc_mcontext.gregs[7],
        (unsigned long) uc->uc_mcontext.gregs[18],
        (unsigned long) uc->uc_mcontext.gregs[17],
        (unsigned long) uc->uc_mcontext.gregs[14],
        (unsigned long) uc->uc_mcontext.gregs[15],
        (unsigned long) uc->uc_mcontext.gregs[3],
        (unsigned long) uc->uc_mcontext.gregs[2],
        (unsigned long) uc->uc_mcontext.gregs[1],
        (unsigned long) uc->uc_mcontext.gregs[0]
    );
    logStackContent((void**)uc->uc_mcontext.gregs[7]);
    #elif defined(__X86_64__) || defined(__x86_64__)
    /* Linux AMD64 */
    serverLog(LL_WARNING,
    "\n"
    "RAX:%016lx RBX:%016lx\nRCX:%016lx RDX:%016lx\n"
    "RDI:%016lx RSI:%016lx\nRBP:%016lx RSP:%016lx\n"
    "R8 :%016lx R9 :%016lx\nR10:%016lx R11:%016lx\n"
    "R12:%016lx R13:%016lx\nR14:%016lx R15:%016lx\n"
    "RIP:%016lx EFL:%016lx\nCSGSFS:%016lx",
        (unsigned long) uc->uc_mcontext.gregs[13],
        (unsigned long) uc->uc_mcontext.gregs[11],
        (unsigned long) uc->uc_mcontext.gregs[14],
        (unsigned long) uc->uc_mcontext.gregs[12],
        (unsigned long) uc->uc_mcontext.gregs[8],
        (unsigned long) uc->uc_mcontext.gregs[9],
        (unsigned long) uc->uc_mcontext.gregs[10],
        (unsigned long) uc->uc_mcontext.gregs[15],
        (unsigned long) uc->uc_mcontext.gregs[0],
        (unsigned long) uc->uc_mcontext.gregs[1],
        (unsigned long) uc->uc_mcontext.gregs[2],
        (unsigned long) uc->uc_mcontext.gregs[3],
        (unsigned long) uc->uc_mcontext.gregs[4],
        (unsigned long) uc->uc_mcontext.gregs[5],
        (unsigned long) uc->uc_mcontext.gregs[6],
        (unsigned long) uc->uc_mcontext.gregs[7],
        (unsigned long) uc->uc_mcontext.gregs[16],
        (unsigned long) uc->uc_mcontext.gregs[17],
        (unsigned long) uc->uc_mcontext.gregs[18]
    );
    logStackContent((void**)uc->uc_mcontext.gregs[15]);
    #endif
#else
    serverLog(LL_WARNING,
        "  Dumping of registers not supported for this OS/arch");
#endif
}

/* Return a file descriptor to write directly to the Redis log with the
 * write(2) syscall, that can be used in critical sections of the code
 * where the rest of Redis can't be trusted (for example during the memory
 * test) or when an API call requires a raw fd.
 *
 * Close it with closeDirectLogFiledes(). */
int openDirectLogFiledes(void) {
    int log_to_stdout = server.logfile[0] == '\0';
    int fd = log_to_stdout ?
        STDOUT_FILENO :
        open(server.logfile, O_APPEND|O_CREAT|O_WRONLY, 0644);
    return fd;
}

/* Used to close what closeDirectLogFiledes() returns. */
void closeDirectLogFiledes(int fd) {
    int log_to_stdout = server.logfile[0] == '\0';
    if (!log_to_stdout) close(fd);
}

/* Logs the stack trace using the backtrace() call. This function is designed
 * to be called from signal handlers safely. */
void logStackTrace(ucontext_t *uc) {
    void *trace[101];
    int trace_size = 0, fd = openDirectLogFiledes();

    if (fd == -1) return; /* If we can't log there is anything to do. */

    /* Generate the stack trace */
    trace_size = backtrace(trace+1, 100);

    if (getMcontextEip(uc) != NULL) {
        char *msg1 = "EIP:\n";
        char *msg2 = "\nBacktrace:\n";
        if (write(fd,msg1,strlen(msg1)) == -1) {/* Avoid warning. */};
        trace[0] = getMcontextEip(uc);
        backtrace_symbols_fd(trace, 1, fd);
        if (write(fd,msg2,strlen(msg2)) == -1) {/* Avoid warning. */};
    }

    /* Write symbols to log file */
    backtrace_symbols_fd(trace+1, trace_size, fd);

    /* Cleanup */
    closeDirectLogFiledes(fd);
}

/* Log information about the "current" client, that is, the client that is
 * currently being served by Redis. May be NULL if Redis is not serving a
 * client right now. */
void logCurrentClient(void) {
    if (server.current_client == NULL) return;

    client *cc = server.current_client;
    sds client;
    int j;

    serverLogRaw(LL_WARNING|LL_RAW, "\n------ CURRENT CLIENT INFO ------\n");
    client = catClientInfoString(sdsempty(),cc);
    serverLog(LL_WARNING|LL_RAW,"%s\n", client);
    sdsfree(client);
    for (j = 0; j < cc->argc; j++) {
        robj *decoded;

        decoded = getDecodedObject(cc->argv[j]);
        serverLog(LL_WARNING|LL_RAW,"argv[%d]: '%s'\n", j,
            (char*)decoded->ptr);
        decrRefCount(decoded);
    }
    /* Check if the first argument, usually a key, is found inside the
     * selected DB, and if so print info about the associated object. */
    if (cc->argc >= 1) {
        robj *val, *key;
        dictEntry *de;

        key = getDecodedObject(cc->argv[1]);
        de = dictFind(cc->db->dict, key->ptr);
        if (de) {
            val = dictGetVal(de);
            serverLog(LL_WARNING,"key '%s' found in DB containing the following object:", (char*)key->ptr);
            serverLogObjectDebugInfo(val);
        }
        decrRefCount(key);
    }
}

#if defined(HAVE_PROC_MAPS)

#define MEMTEST_MAX_REGIONS 128

/* A non destructive memory test executed during segfauls. */
int memtest_test_linux_anonymous_maps(void) {
    FILE *fp;
    char line[1024];
    char logbuf[1024];
    size_t start_addr, end_addr, size;
    size_t start_vect[MEMTEST_MAX_REGIONS];
    size_t size_vect[MEMTEST_MAX_REGIONS];
    int regions = 0, j;

    int fd = openDirectLogFiledes();
    if (!fd) return 0;

    fp = fopen("/proc/self/maps","r");
    if (!fp) return 0;
    while(fgets(line,sizeof(line),fp) != NULL) {
        char *start, *end, *p = line;

        start = p;
        p = strchr(p,'-');
        if (!p) continue;
        *p++ = '\0';
        end = p;
        p = strchr(p,' ');
        if (!p) continue;
        *p++ = '\0';
        if (strstr(p,"stack") ||
            strstr(p,"vdso") ||
            strstr(p,"vsyscall")) continue;
        if (!strstr(p,"00:00")) continue;
        if (!strstr(p,"rw")) continue;

        start_addr = strtoul(start,NULL,16);
        end_addr = strtoul(end,NULL,16);
        size = end_addr-start_addr;

        start_vect[regions] = start_addr;
        size_vect[regions] = size;
        snprintf(logbuf,sizeof(logbuf),
            "*** Preparing to test memory region %lx (%lu bytes)\n",
                (unsigned long) start_vect[regions],
                (unsigned long) size_vect[regions]);
        if (write(fd,logbuf,strlen(logbuf)) == -1) { /* Nothing to do. */ }
        regions++;
    }

    int errors = 0;
    for (j = 0; j < regions; j++) {
        if (write(fd,".",1) == -1) { /* Nothing to do. */ }
        errors += memtest_preserving_test((void*)start_vect[j],size_vect[j],1);
        if (write(fd, errors ? "E" : "O",1) == -1) { /* Nothing to do. */ }
    }
    if (write(fd,"\n",1) == -1) { /* Nothing to do. */ }

    /* NOTE: It is very important to close the file descriptor only now
     * because closing it before may result into unmapping of some memory
     * region that we are testing. */
    fclose(fp);
    closeDirectLogFiledes(fd);
    return errors;
}
#endif

/* Scans the (assumed) x86 code starting at addr, for a max of `len`
 * bytes, searching for E8 (callq) opcodes, and dumping the symbols
 * and the call offset if they appear to be valid. */
void dumpX86Calls(void *addr, size_t len) {
    size_t j;
    unsigned char *p = addr;
    Dl_info info;
    /* Hash table to best-effort avoid printing the same symbol
     * multiple times. */
    unsigned long ht[256] = {0};

    if (len < 5) return;
    for (j = 0; j < len-4; j++) {
        if (p[j] != 0xE8) continue; /* Not an E8 CALL opcode. */
        unsigned long target = (unsigned long)addr+j+5;
        target += *((int32_t*)(p+j+1));
        if (dladdr((void*)target, &info) != 0 && info.dli_sname != NULL) {
            if (ht[target&0xff] != target) {
                printf("Function at 0x%lx is %s\n",target,info.dli_sname);
                ht[target&0xff] = target;
            }
            j += 4; /* Skip the 32 bit immediate. */
        }
    }
}

void sigsegvHandler(int sig, siginfo_t *info, void *secret) {
    ucontext_t *uc = (ucontext_t*) secret;
    void *eip = getMcontextEip(uc);
    sds infostring, clients;
    struct sigaction act;
    UNUSED(info);

    bugReportStart();
    serverLog(LL_WARNING,
        "Redis %s crashed by signal: %d", REDIS_VERSION, sig);
    if (eip != NULL) {
        serverLog(LL_WARNING,
        "Crashed running the instuction at: %p", eip);
    }
    if (sig == SIGSEGV || sig == SIGBUS) {
        serverLog(LL_WARNING,
        "Accessing address: %p", (void*)info->si_addr);
    }
    serverLog(LL_WARNING,
        "Failed assertion: %s (%s:%d)", server.assert_failed,
                        server.assert_file, server.assert_line);

    /* Log the stack trace */
    serverLogRaw(LL_WARNING|LL_RAW, "\n------ STACK TRACE ------\n");
    logStackTrace(uc);

    /* Log INFO and CLIENT LIST */
    serverLogRaw(LL_WARNING|LL_RAW, "\n------ INFO OUTPUT ------\n");
    infostring = genRedisInfoString("all");
    infostring = sdscatprintf(infostring, "hash_init_value: %u\n",
        dictGetHashFunctionSeed());
    serverLogRaw(LL_WARNING|LL_RAW, infostring);
    serverLogRaw(LL_WARNING|LL_RAW, "\n------ CLIENT LIST OUTPUT ------\n");
    clients = getAllClientsInfoString();
    serverLogRaw(LL_WARNING|LL_RAW, clients);
    sdsfree(infostring);
    sdsfree(clients);

    /* Log the current client */
    logCurrentClient();

    /* Log dump of processor registers */
    logRegisters(uc);

#if defined(HAVE_PROC_MAPS)
    /* Test memory */
    serverLogRaw(LL_WARNING|LL_RAW, "\n------ FAST MEMORY TEST ------\n");
    bioKillThreads();
    if (memtest_test_linux_anonymous_maps()) {
        serverLogRaw(LL_WARNING|LL_RAW,
            "!!! MEMORY ERROR DETECTED! Check your memory ASAP !!!\n");
    } else {
        serverLogRaw(LL_WARNING|LL_RAW,
            "Fast memory test PASSED, however your memory can still be broken. Please run a memory test for several hours if possible.\n");
    }
#endif

    if (eip != NULL) {
        Dl_info info;
        if (dladdr(eip, &info) != 0) {
            serverLog(LL_WARNING|LL_RAW,
                "\n------ DUMPING CODE AROUND EIP ------\n"
                "Symbol: %s (base: %p)\n"
                "Module: %s (base %p)\n"
                "$ xxd -r -p /tmp/dump.hex /tmp/dump.bin\n"
                "$ objdump --adjust-vma=%p -D -b binary -m i386:x86-64 /tmp/dump.bin\n"
                "------\n",
                info.dli_sname, info.dli_saddr, info.dli_fname, info.dli_fbase,
                info.dli_saddr);
            size_t len = (long)eip - (long)info.dli_saddr;
            unsigned long sz = sysconf(_SC_PAGESIZE);
            if (len < 1<<13) { /* we don't have functions over 8k (verified) */
                /* Find the address of the next page, which is our "safety"
                 * limit when dumping. Then try to dump just 128 bytes more
                 * than EIP if there is room, or stop sooner. */
                unsigned long next = ((unsigned long)eip + sz) & ~(sz-1);
                unsigned long end = (unsigned long)eip + 128;
                if (end > next) end = next;
                len = end - (unsigned long)info.dli_saddr;
                serverLogHexDump(LL_WARNING, "dump of function",
                    info.dli_saddr ,len);
                dumpX86Calls(info.dli_saddr,len);
            }
        }
    }

    serverLogRaw(LL_WARNING|LL_RAW,
"\n=== REDIS BUG REPORT END. Make sure to include from START to END. ===\n\n"
"       Please report the crash by opening an issue on github:\n\n"
"           http://github.com/antirez/redis/issues\n\n"
"  Suspect RAM error? Use redis-server --test-memory to verify it.\n\n"
);

    /* free(messages); Don't call free() with possibly corrupted memory. */
    if (server.daemonize && server.supervised == 0) unlink(server.pidfile);

    /* Make sure we exit with the right signal at the end. So for instance
     * the core will be dumped if enabled. */
    sigemptyset (&act.sa_mask);
    act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND;
    act.sa_handler = SIG_DFL;
    sigaction (sig, &act, NULL);
    kill(getpid(),sig);
}
#endif /* HAVE_BACKTRACE */

/* ==================== Logging functions for debugging ===================== */

void serverLogHexDump(int level, char *descr, void *value, size_t len) {
    char buf[65], *b;
    unsigned char *v = value;
    char charset[] = "0123456789abcdef";

    serverLog(level,"%s (hexdump of %zu bytes):", descr, len);
    b = buf;
    while(len) {
        b[0] = charset[(*v)>>4];
        b[1] = charset[(*v)&0xf];
        b[2] = '\0';
        b += 2;
        len--;
        v++;
        if (b-buf == 64 || len == 0) {
            serverLogRaw(level|LL_RAW,buf);
            b = buf;
        }
    }
    serverLogRaw(level|LL_RAW,"\n");
}

/* =========================== Software Watchdog ============================ */
#include <sys/time.h>

void watchdogSignalHandler(int sig, siginfo_t *info, void *secret) {
#ifdef HAVE_BACKTRACE
    ucontext_t *uc = (ucontext_t*) secret;
#endif
    UNUSED(info);
    UNUSED(sig);

    serverLogFromHandler(LL_WARNING,"\n--- WATCHDOG TIMER EXPIRED ---");
#ifdef HAVE_BACKTRACE
    logStackTrace(uc);
#else
    serverLogFromHandler(LL_WARNING,"Sorry: no support for backtrace().");
#endif
    serverLogFromHandler(LL_WARNING,"--------\n");
}

/* Schedule a SIGALRM delivery after the specified period in milliseconds.
 * If a timer is already scheduled, this function will re-schedule it to the
 * specified time. If period is 0 the current timer is disabled. */
void watchdogScheduleSignal(int period) {
    struct itimerval it;

    /* Will stop the timer if period is 0. */
    it.it_value.tv_sec = period/1000;
    it.it_value.tv_usec = (period%1000)*1000;
    /* Don't automatically restart. */
    it.it_interval.tv_sec = 0;
    it.it_interval.tv_usec = 0;
    setitimer(ITIMER_REAL, &it, NULL);
}

/* Enable the software watchdog with the specified period in milliseconds. */
void enableWatchdog(int period) {
    int min_period;

    if (server.watchdog_period == 0) {
        struct sigaction act;

        /* Watchdog was actually disabled, so we have to setup the signal
         * handler. */
        sigemptyset(&act.sa_mask);
        act.sa_flags = SA_ONSTACK | SA_SIGINFO;
        act.sa_sigaction = watchdogSignalHandler;
        sigaction(SIGALRM, &act, NULL);
    }
    /* If the configured period is smaller than twice the timer period, it is
     * too short for the software watchdog to work reliably. Fix it now
     * if needed. */
    min_period = (1000/server.hz)*2;
    if (period < min_period) period = min_period;
    watchdogScheduleSignal(period); /* Adjust the current timer. */
    server.watchdog_period = period;
}

/* Disable the software watchdog. */
void disableWatchdog(void) {
    struct sigaction act;
    if (server.watchdog_period == 0) return; /* Already disabled. */
    watchdogScheduleSignal(0); /* Stop the current timer. */

    /* Set the signal handler to SIG_IGN, this will also remove pending
     * signals from the queue. */
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    act.sa_handler = SIG_IGN;
    sigaction(SIGALRM, &act, NULL);
    server.watchdog_period = 0;
}

vscode 启动配置

在redis根目录下创建.vscode文件夹并创建launch.json键入如下配置：

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        
        {
            "name": "(lldb Launch)", // 名字随便取
            "type": "cppdbg",
            "request": "launch",
            // 可执行程序位置，这里我们启动 redis 服务端
            "program": "${workspaceFolder}/src/redis-server", 
            // 程序参数
            "args": [ 
                // 例如：使用配置文件启动
                // "/path/to/your/redis.conf"
            ],
            "stopAtEntry": false,
            // 可执行程序的工作目录，也可以使用绝对路径
            "cwd": "${fileDirname}", 
            "environment": [],
            "externalConsole": false,
            "MIMode": "lldb",
            "setupCommands": [
                {
                  "description": "Enable pretty-printing",
                  "text": "-enable-pretty-printing",
                  "ignoreFailures": true
                }
            ]
        }
    ]
}

最终效果

完成上述的基本配置后，我们找到server.c,找到我们刚刚配置的选项将redis启动：

项目启动成功，我们就可以愉快的调试代码了：

关于vscode调试代码卡死问题

这也是笔者近期的一段经历，在通过vscode调试redis代码时出现了一次彩虹转圈，但是其余软件使用都是良好，大概率推测时vscode配置的问题，查阅网上资料结合笔者个人排查来看，大体是配置不当导致code helper飙高导致的，而解决的办法也很简单，找到vscode的setting.json补充如下内容，告知vscode无视符号连接，仅检索当前工程里的真实文件：

 "search.followSymlinks": false,
    "files.exclude": {
        "**/.git": true,
        "**/.svn": true,
        "**/.hg": true,
        "**/CVS": true,
        "**/.DS_Store": true,
        "**/tmp": true,
        "**/node_modules": true,
        "**/bower_components": true,
        "**/dist": true
    },
    "files.watcherExclude": {
        "**/.git/objects/**": true,
        "**/.git/subtree-cache/**": true,
        "**/node_modules/**": true,
        "**/tmp/**": true,
        "**/bower_components/**": true,
        "**/dist/**": true
    }

小结

本文算是笔者对于redis源码解读系列的开篇，感兴趣的读者可以按照笔者的配置步骤搭建一套redis源码调试环境，笔者会在此基础上整理一些redis源码的解读文章，希望对你有帮助。

我是 SharkChili，Java 开发者，Java Guide开源项目维护者。欢迎关注我的公众号：写代码的SharkChili，也欢迎您了解我的开源项目 mini-redis：https://github.com/shark-ctrl/mini-redis。

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参考

Redis debug:https://github.com/wenfh2020/youtobe/blob/master/redis-debug.md (opens new window)

WSL官方文档:https://learn.microsoft.com/zh-cn/windows/wsl/tutorials/wsl-vscode (opens new window)

redis 安装报错 jemalloc/jemalloc.h: No such file or directory:https://www.cnblogs.com/oxspirt/p/11392437.html (opens new window)

VSCode配置说明:https://code.visualstudio.com/docs/cpp/launch-json-reference (opens new window)

Mac/Linux 下使用 vscode 调试 redis 源码（超方便）：https://juejin.cn/post/7267158769490264104 (opens new window)

redis 3.2.13 build error on arm64 mac OS Monterey #10420:https://github.com/redis/redis/issues/10420 (opens new window)

mac上编译redis ，报错fstat64:https://blog.csdn.net/wbo112/article/details/141526182 (opens new window)

mac中Code Helper进程占用大量CPU和内存:https://juejin.cn/post/6860402160199270408 (opens new window)

如何打开并且配置vscode的setting.json文件:https://blog.csdn.net/daishu_shu/article/details/131439706 (opens new window)