stackwalk (Stack walk utility)
Description

The stackwalk command in VSDebugPro performs a structured dump of the call stack for the current thread or all threads in the debugged process. It provides a detailed view of the program’s execution state, which is crucial for understanding the flow of control and diagnosing issues.

Syntax

stackwalk [-o <filename>] [depth] [all]
Parameters
  • -o <filename>: Optional. Specifies the output file to write the stack dump. If not provided, the output is displayed in the console.
  • depth: Optional. Specifies the number of frames to dump per thread. If not provided, all frames are dumped.
  • all: Optional. If specified, dumps the stack for all threads. Otherwise, only the current thread’s stack is dumped.
Usage Examples

  1. Dump current thread’s stack to console:

    stackwalk

  2. Dump current thread’s stack to a file:

    stackwalk -o stack.txt

  3. Dump the first 10 frames of the current thread’s stack:

    stackwalk 10

  4. Dump all threads’ stacks to a file:

    stackwalk -o allstacks.txt all

  5. Dump the first 5 frames of all threads’ stacks:

    stackwalk -o stacks.txt 5 all

Sample code

#include <Windows.h>
#include <string>
#include <iostream>

void five(const std::string& msg, int depth) {
    depth++;
    std::cout << msg << std::endl;
}

void four(const std::string& msg, int depth) {
    depth++;
    five(msg, depth);
}

void three(const std::string& msg, int depth) {
    depth++;
    four(msg, depth);
}

void two(const std::string& msg, int depth) {
    depth++;
    three(msg, depth);
}

void one(const std::string& msg, int depth) {
    depth++;
    two(msg, depth);
}

int main()
{
    int depth = 0;
    one("callstack", depth);

    return 0;
}

Stack trace in function five:

Stack Dump:
===========
Thread ID: 14520, Name: 
-------------------------------------------
Frame 0:
  Function: five
  Local Variables:
    depth = 5 (int)
    msg = "callstack" (const std::string &)
  Parameters:
    msg = {...} (const std::string &)
    depth = 5 (int)

Frame 1:
  Function: four
  Local Variables:
    depth = 4 (int)
    msg = "callstack" (const std::string &)
  Parameters:
    msg = {...} (const std::string &)
    depth = 4 (int)

Frame 2:
  Function: three
  Local Variables:
    depth = 3 (int)
    msg = "callstack" (const std::string &)
  Parameters:
    msg = {...} (const std::string &)
    depth = 3 (int)

Frame 3:
  Function: two
  Local Variables:
    depth = 2 (int)
    msg = "callstack" (const std::string &)
  Parameters:
    msg = {...} (const std::string &)
    depth = 2 (int)

Frame 4:
  Function: one
  Local Variables:
    depth = 1 (int)
    msg = "callstack" (const std::string &)
  Parameters:
    msg = {...} (const std::string &)
    depth = 1 (int)

Frame 5:
  Function: main
  Local Variables:
    depth = 0 (int)
  Parameters:
Notes
  • The stackwalk command requires the debugger to be in break mode. If the debugger is running, the command will fail.
  • Symbol information must be available for best results. Without symbols, some information (like function names and source locations) may be missing.
  • The depth of the stack dump may be limited by the debugger or the process being debugged.
  • Large stack dumps, especially when dumping all threads, can take some time to generate.
Best Practices
  1. Start with dumping only the current thread’s stack before exploring all threads.
  2. Use a reasonable depth limit when dealing with deep recursion or very large call stacks.
  3. When investigating a specific issue, focus on the relevant threads rather than dumping all threads.
  4. Save stack dumps to files for later analysis or comparison.
Troubleshooting
  • If the output lacks detailed information, ensure that debug symbols are loaded correctly.
  • If the command fails, make sure the debugger is in break mode and attached to a process.
  • For very large applications with many threads, consider using depth limits to avoid excessive output.

By using the stackwalk command effectively, you can gain valuable insights into your program’s execution state, making it easier to track down bugs and understand complex control flows.