为了在运行时捕获诸如段错误之类的致命错误,我编写了一个自定义 SignalHandler,它将堆栈跟踪打印到控制台和日志文件中。

为了实现这一点,我使用(在我之前的数百个) backtrace()backtrace_symbols() 函数与 addr2line 结合使用。

backtrace_symbols() 的调用产生以下输出:

Obtained 8 stack frames.
./Mainboard_Software(+0xb1af5) [0x56184991baf5]
./Mainboard_Software(+0xb1a79) [0x56184991ba79]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x12dd0) [0x7fe72948bdd0]
./Mainboard_Software(causeSIGFPE+0x16) [0x561849918a10]
./Mainboard_Software(_Z13MainboardInit7QString+0xf3) [0x56184990e0df]
./Mainboard_Software(main+0x386) [0x5618499182a3]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xeb) [0x7fe727fd909b]
./Mainboard_Software(_start+0x2a) [0x5618498ff0aa]

我需要将偏移量传递给 addr2line 以获取我的模块名称和行号。
$ addr2line -C -a -s -f -p -e ./D098_Mainboard_Software 0xb1a79
0x00000000000b1a79: HandleBacktraceSignals at SignalModule.c:492

但是,在某些模块(尤其是 cpp 模块)中,我将偏移量作为 sybols 和 hex 的组合,例如 _Z13MainboardInit7QString+0xf3
我可以通过调用 nm 将符号解析为十六进制:
$ nm Mainboard_Software | grep _Z13MainboardInit7QString
00000000000a3fec T _Z13MainboardInit7QString

现在我可以添加这两个十六进制数字,将它们传递给 addr2line 并获取我的模块名称和行号,如果我想,甚至可以取消:
$ addr2line -C -a -s -f -p -e ./D098_Mainboard_Software 0xa40df
0x00000000000a40df: MainboardInit(QString) at MainboardInit.cpp:219

但我想在运行时执行最后两个步骤。有没有办法在运行时解析这些符号(例如 _Z13MainboardInit7QString+0xf3 ),以便我可以将它们直接传递给 addr2line?
我的程序由 .c 和 .cpp 模块组成。

最佳答案

我花了一段时间,但对于 Linux,可以使用 dlfcn.h GNU 库。
只要确保在所有头文件包含的上方定义 _GNU_SOURCE 即可。
请注意,此包含将使您的程序不符合 POSIX。

对于链接器标志,为两种体系结构添加 -ldl ,为 x86 添加 -g3 ,为 ARM 添加 -g3-funwind-tables-mapcs-frame

#define _GNU_SOURCE

#include <execinfo.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#include <dlfcn.h>
#include <gnu/lib-names.h>

#define STACK_FRAMES_BUFFERSIZE (int)128

static void * STACK_FRAMES_BUFFER[128];
static void * OFFSET_FRAMES_BUFFER[128];
static char   EXECUTION_FILENAME[32] = "Mainboard_Software";


/*-----------------------------------------------------------------------------------*/
/*
 * Function will attempt to backtrace the signal cause by collecting the last called addresses.
 * The addresses will then be translated into readable stings by addr2line
 */

static void PrintBacktrace(void)
{
   const char errorString[] = "Offset cannot be resolved: No offset present?\n\0?";
   char       printArray[100] = {0};
   size_t     bufferEntries;
   char **    stackFrameStrings;
   size_t     frameIterator;

   //backtrace the last calls
   bufferEntries = backtrace(STACK_FRAMES_BUFFER, STACK_FRAMES_BUFFERSIZE);
   stackFrameStrings = backtrace_symbols(STACK_FRAMES_BUFFER, (int)bufferEntries);

   //print the number of obtained frames
  sprintf(printArray,"\nObtained %zd stack frames.\n\r", bufferEntries);
  (void)write(STDERR_FILENO, printArray, strlen(printArray));

   //iterate over addresses and print the stings
   for (frameIterator = 0; frameIterator < bufferEntries; frameIterator++)
   {
#if __x86_64__
      //calculate the offset on x86_64 and print the file and line number with addr2line
      OFFSET_FRAMES_BUFFER[frameIterator] = CalculateOffset(stackFrameStrings[frameIterator]);
      if(OFFSET_FRAMES_BUFFER[frameIterator] == NULL)
      {
         (void)write(STDERR_FILENO, errorString, strlen(errorString));
      }
      else
      {
         Addr2LinePrint(OFFSET_FRAMES_BUFFER[frameIterator]);
      }
#endif
#if __arm__
      //the address itself can be used on ARM for a call to addr2line
      Addr2LinePrint(STACK_FRAMES_BUFFER[frameIterator]);
#endif
   }
   free (stackFrameStrings);
 }

/*-----------------------------------------------------------------------------------*/
/*
 * Use add2line on the obtained addresses to get a readable sting
 */
static void Addr2LinePrint(void const * const addr)
{
  char addr2lineCmd[512] = {0};

  //have addr2line map the address to the relent line in the code
  (void)sprintf(addr2lineCmd,"addr2line -C -i -f -p -s -a -e ./%s %p ", EXECUTION_FILENAME, addr);

  //This will print a nicely formatted string specifying the function and source line of the address
  (void)system(addr2lineCmd);
}
/*-----------------------------------------------------------------------------------*/
/*
 * Pass a string which was returned by a call to backtrace_symbols() to get the total offset
 * which might be decoded as (symbol + offset). This function will return the calculated offset
 * as void pointer, this pointer can be passed to addr2line in a following call.
 */
void *  CalculateOffset(char * stackFrameString)
{
   void *     objectFile;
   void *     address;
   void *     offset = NULL;
   char       symbolString[75] = {'\0'};
   char       offsetString[25] = {'\0'};
   char *      dlErrorSting;
   int        checkSscanf = EOF;
   int        checkDladdr = 0;
   Dl_info    symbolInformation;

   //parse the string obtained by backtrace_symbols() to get the symbol and offset
   parseStrings(stackFrameString, symbolString, offsetString);

   //convert the offset from a string to a pointer
   checkSscanf = sscanf(offsetString, "%p",&offset);

   //check if a symbol string was created,yes, convert symbol string to offset
   if(symbolString[0] != '\0')
   {
      //open the object (if NULL the executable itself)
      objectFile = dlopen(NULL, RTLD_LAZY);
      //check for error
      if(!objectFile)
      {
         dlErrorSting = dlerror();
         (void)write(STDERR_FILENO, dlErrorSting, strlen(dlErrorSting));
      }
      //convert sting to a address
      address = dlsym(objectFile, symbolString);
      //check for error
      if(address == NULL)
      {
         dlErrorSting = dlerror();
         (void)write(STDERR_FILENO, dlErrorSting, strlen(dlErrorSting));
      }
      //extract the symbolic information pointed by address
      checkDladdr = dladdr(address, &symbolInformation);

      if(checkDladdr != 0)
      {
         //calculate total offset of the symbol
         offset = (symbolInformation.dli_saddr - symbolInformation.dli_fbase) + offset;
         //close the object
         dlclose(objectFile);
      }
      else
      {
         dlErrorSting = dlerror();
         (void)write(STDERR_FILENO, dlErrorSting, strlen(dlErrorSting));
      }
   }

   return checkSscanf != EOF ? offset : NULL;
}
/*-----------------------------------------------------------------------------------*/
/*
 * Parse a string which was returned from backtrace_symbols() to get the symbol name
 * and the offset.
 */

void parseStrings(char * stackFrameString, char * symbolString, char * offsetString)
{
   char *        symbolStart = NULL;
   char *        offsetStart = NULL;
   char *        offsetEnd = NULL;
   unsigned char stringIterator = 0;

   //iterate over the string and search for special characters
   for(char * iteratorPointer = stackFrameString; *iteratorPointer; iteratorPointer++)
   {
      //The '(' char indicates the beginning of the symbol
      if(*iteratorPointer == '(')
      {
         symbolStart = iteratorPointer;
      }
      //The '+' char indicates the beginning of the offset
      else if(*iteratorPointer == '+')
      {
         offsetStart = iteratorPointer;
      }
      //The ')' char indicates the end of the offset
      else if(*iteratorPointer == ')')
      {
         offsetEnd = iteratorPointer;
      }

   }
   //Copy the symbol string into an array pointed by symbolString
   for(char * symbolPointer = symbolStart+1; symbolPointer != offsetStart; symbolPointer++)
   {
      symbolString[stringIterator] = *symbolPointer;
      ++stringIterator;
   }
   //Reset string iterator for the new array which will be filled
   stringIterator = 0;
   //Copy the offset string into an array pointed by offsetString
   for(char * offsetPointer = offsetStart+1; offsetPointer != offsetEnd; offsetPointer++)
   {
      offsetString[stringIterator] = *offsetPointer;
      ++stringIterator;
   }
}


调用此函数将在控制台上产生如下输出:
Obtained 11 stack frames.
0x00000000000b1ba5: PrintBacktrace at SignalModule.c:524
0x00000000000b1aeb: HandleBacktraceSignals at SignalModule.c:494
0x0000000000012dd0: ?? ??:0
0x00000000000aea85: baz at testFunctions.c:75
0x00000000000aea6b: bar at testFunctions.c:70
0x00000000000aea5f: foo at testFunctions.c:65
0x00000000000aea53: causeSIGSEGV at testFunctions.c:53
0x00000000000a412f: MainboardInit(QString) at MainboardInit.cpp:218
0x00000000000ae2f3: main at Main.cpp:142 (discriminator 2)
0x000000000002409b: ?? ??:0
0x00000000000950fa: _start at ??:?

关于c++ - 在 addr2line 的运行时,ro 如何从偏移量中的 backtrace_symbols() 解析 cpp 符号,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/55450932/

10-11 15:38