解决backward-cpp交叉编译时无法打印文件名、行号的问题
2026-01-16 23:59:40 #C++

程序有时候会崩溃退出，完全不知道是哪里崩的，一点信息都没有。于是找到了 backward-cpp 这个项目，它使用非常简单，跨平台支持的不错。

但是我在Linux下使用时无法打印源文件名，折腾了好几个小时才找到原因：因为我是在Windows下交叉编译的，而backward-cpp的cmake配置中会自动检测dw、dwarf和bfd，显然在Windows下是没有这些库的，于是崩溃时只能打印内存地址。

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Stack trace (most recent call last):
#4    Object "[0xffffffffffffffff]", at 0xffffffffffffffff, in 
#3    Object "./DemoServer", at 0x415838, in 
#2    Object "/lib/x86_64-linux-gnu/libc.so.6", at 0x7f4eefe5483f, in __libc_start_main
#1    Object "./DemoServer", at 0x41576f, in 
#0    Object "./DemoServer", at 0x415f13, in 
Segmentation fault (Address not mapped to object [(nil)])

#方案一：在Windows下连接libdwarf, libelf, libdl等库

在Linux下安装相关的库，然后将头文件和库文件拷贝到Windows上，再到CMake中链接也是可以的，但这会陷入依赖地狱，非常折腾。

#方案二：用addr2line

仅依赖addr2line命令，这样在Windows上编译时就是零依赖，只需要修改下backward的源码即可。

首先，不再用库自带的CMake配置了，直接下载backward.hpp引入到项目中。
然后写个简单的target：

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set(TARGET_NAME backward)

add_library(${TARGET_NAME} INTERFACE)

target_include_directories(${TARGET_NAME} INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})

target_compile_definitions(${TARGET_NAME} INTERFACE
        BACKWARD_HAS_DW=0
        BACKWARD_HAS_BFD=0
        BACKWARD_HAS_DWARF=0
)

修改TraceResolverLinuxImpl<trace_resolver_tag::backtrace_symbol>::resolve方法。
之前：

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ResolvedTrace resolve(ResolvedTrace trace) override {
    char *filename = _symbols[trace.idx];
    char *funcname = filename;
    while (*funcname && *funcname != '(') {
      funcname += 1;
    }
    trace.object_filename.assign(filename,
                                 funcname); // ok even if funcname is the ending
                                            // \0 (then we assign entire string)

    if (*funcname) { // if it's not end of string (e.g. from last frame ip==0)
      funcname += 1;
      char *funcname_end = funcname;
      while (*funcname_end && *funcname_end != ')' && *funcname_end != '+') {
        funcname_end += 1;
      }
      *funcname_end = '\0';
      trace.object_function = this->demangle(funcname);
      trace.source.function = trace.object_function; // we cannot do better.
    }
    return trace;
  }

修改后：

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ResolvedTrace resolve(ResolvedTrace trace) override {
    char cmd[1024];
    char self_path[PATH_MAX] = {0};

    ssize_t len = ::readlink("/proc/self/exe", self_path, sizeof(self_path) - 1);

    if (len > 0) {
        self_path[len] = '\0';
    } else {
        FILE* f = fopen("/proc/self/cmdline", "rb");
        if (f) {
            size_t n = fread(self_path, 1, sizeof(self_path) - 1, f);
            if (n > 0) {
                self_path[n] = '\0';
            }
            fclose(f);
        }
    }

    if (self_path[0] == 0) {
        if (_symbols) {
            char *filename = _symbols[trace.idx];
            trace.object_filename = filename ? filename : "unknown";
        }
        return trace;
    }

    snprintf(cmd, sizeof(cmd), "/usr/bin/addr2line -e \"%s\" -f -C 0x%lx", self_path, (unsigned long)trace.addr);

    FILE* fp = popen(cmd, "r");
    if (fp) {
        char func_buf[1024] = {0};
        char file_buf[1024] = {0};

        char* line1 = fgets(func_buf, sizeof(func_buf), fp);
        char* line2 = fgets(file_buf, sizeof(file_buf), fp);

        if (line1 && line2) {
            size_t l = strlen(func_buf);
            if (l > 0 && func_buf[l-1] == '\n') func_buf[l-1] = 0;

            l = strlen(file_buf);
            if (l > 0 && file_buf[l-1] == '\n') file_buf[l-1] = 0;

            trace.object_function = func_buf;
            trace.source.function = func_buf;

            std::string file_line = file_buf;
            size_t colon_pos = file_line.find_last_of(':');
            if (colon_pos != std::string::npos) {
                trace.source.filename = file_line.substr(0, colon_pos);
                try {
                    trace.source.line = std::stoi(file_line.substr(colon_pos + 1));
                } catch (...) { trace.source.line = 0; }
            } else {
                trace.source.filename = file_line;
            }
        }
        pclose(fp);
        return trace;
    }

    if (_symbols) {
        char *filename = _symbols[trace.idx];
        trace.object_filename = filename ? filename : "unknown";
    }
    return trace;
  }

再次测试：

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Stack trace (most recent call last):
#4    Source "??", line 0, in ?? [0xffffffffffffffff]
#3    Source "/opt/glibc-2.23/csu/../sysdeps/x86_64/start.S", line 118, in _start [0x415978]
#2    Source "??", line 0, in ?? [0x7f3c4eddc082]
#1    Source "C:\work\code\MyApp\cmake-build-relwithdebinfo-linux-x86_64/C:/work/code/MyApp/src/Demo/Server/src/main.cpp", line 117, in main [0x4158af]
#0    Source "C:\work\code\MyApp\cmake-build-relwithdebinfo-linux-x86_64/C:/work/code/MyApp/src/Demo/Server/src/main.cpp", line 101, in cause_crash() [0x416053]
Segmentation fault (Address not mapped to object [(nil)])
Segmentation fault (core dumped)

可以看到源文件名和行号都能打印了，只是这个路径还是Windows下的，这个可以用-fdebug-prefix-map编译选项来优化一下

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add_compile_options("-fdebug-prefix-map=${CMAKE_SOURCE_DIR}=")

这样就变成相对路径了，完美了

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Stack trace (most recent call last):
#4    Source "??", line 0, in ?? [0xffffffffffffffff]
#3    Source "/opt/glibc-2.23/csu/../sysdeps/x86_64/start.S", line 118, in _start [0x415978]
#2    Source "??", line 0, in ?? [0x7fb465c5d082]
#1    Source "/src/Demo/Server/src/main.cpp", line 117, in main [0x4158af]
#0    Source "/src/Demo/Server/src/main.cpp", line 101, in cause_crash() [0x416053]
Segmentation fault (Address not mapped to object [(nil)])
Segmentation fault (core dumped)
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