How to get a stack trace for C++ using gcc with line number information?

Question

We use stack traces in proprietary assert like macro to catch developer mistakes - when error is caught, stack trace is printed.

I find gcc\'s pair

Answer 1

I had to do this in a production environment with many constraints, so I wanted to explain the advantages and disadvantages of the already posted methods.

1. attach GDB

+ very simple and robust

- Slow for large programs because GDB insists on loading the entire address to line # database upfront instead of lazily

- Interferes with signal handling. When GDB is attached, it intercepts signals like SIGINT (ctrl-c), which will cause the program to get stuck at the GDB interactive prompt? if some other process routinely sends such signals. Maybe there's some way around it, but this made GDB unusable in my case. You can still use it if you only care about printing a call stack once when your program crashes, but not multiple times.

2. addr2line. Here's an alternate solution that doesn't use backtrace_symbols.

+ Doesn't allocate from the heap, which is unsafe inside a signal handler

+ Don't need to parse output of backtrace_symbols

- Won't work on MacOS, which doesn't have dladdr1. You can use _dyld_get_image_vmaddr_slide instead, which returns the same offset as link_map::l_addr.

- Requires adding negative offset or else the translated line # will be 1 greater. backtrace_symbols does this for you

#include 
#include 
#include 
#include 

// converts a function's address in memory to its VMA address in the executable file. VMA is what addr2line expects
size_t ConvertToVMA(size_t addr)
{
  Dl_info info;
  link_map* link_map;
  dladdr1((void*)addr,&info,(void**)&link_map,RTLD_DL_LINKMAP);
  return addr-link_map->l_addr;
}

void PrintCallStack()
{
  void *callstack[128];
  int frame_count = backtrace(callstack, sizeof(callstack)/sizeof(callstack[0]));
  for (int i = 0; i < frame_count; i++)
  {
    char location[1024];
    Dl_info info;
    if(dladdr(callstack[i],&info))
    {
      char command[256];
      size_t VMA_addr=ConvertToVMA((size_t)callstack[i]);
      //if(i!=crash_depth)
        VMA_addr-=1;    // https://stackoverflow.com/questions/11579509/wrong-line-numbers-from-addr2line/63841497#63841497
      snprintf(command,sizeof(command),"addr2line -e %s -Ci %zx",info.dli_fname,VMA_addr);
      system(command);
    }
  }
}

void Foo()
{
  PrintCallStack();
}

int main()
{
  Foo();
  return 0;
}

I also want to clarify what addresses backtrace and backtrace_symbols generate and what addr2line expects. addr2line expects Foo_VMA or if you're using --section=.text, then Foo_file - text_file. backtrace returns Foo_mem. backtrace_symbols generates Foo_VMA somewhere. One big mistake I made and saw in several other posts was assuming VMA_base = 0 or Foo_VMA = Foo_file = Foo_mem - ELF_mem, which is easy to calculate. That often works, but for some compilers (i.e. linker scripts) use VMA_base > 0. Examples would be the GCC 5.4 on Ubuntu 16 (0x400000) and clang 11 on MacOS (0x100000000). For shared libs, it's always 0. Seems VMAbase was only meaningful for non-position independent code. Otherwise it has no effect on where the EXE is loaded in memory.

Also, neither karlphillip's nor this one requires compiling with -rdynamic. That will increase the binary size, especially for a large C++ program or shared lib, with useless entries in the dynamic symbol table that never get imported