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print_stacktrace_glibc: fixes

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- do not write trailing NULL byte
- do not use snprintf - is not async-signal-safe
- added a bit Doxy docu
This commit is contained in:
Martin Pulec
2025-08-13 12:12:15 +02:00
parent 2b3ae39a4f
commit 9a2956ef34
1 changed files with 20 additions and 5 deletions
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25
src/host.cpp
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@@ -1255,7 +1255,12 @@ bool running_in_debugger(){
}
#if defined(__GLIBC__)
/// print stacktrace with backtrace_symbols_fd() (glibc or macOS)
/**
* print stacktrace with backtrace_symbols_fd() (glibc or macOS)
*
* ideally all functions should be async-signal-safe as defined by POSIX
* (glibc deviates sligntly, see also signal-safety(7))
*/
static void
print_stacktrace_glibc()
{
@@ -1266,11 +1271,21 @@ print_stacktrace_glibc()
#else
char path[MAX_PATH_SIZE];
#ifdef __APPLE__
const unsigned long tid = pthread_mach_thread_np(pthread_self());
unsigned long tid = pthread_mach_thread_np(pthread_self());
#else
const unsigned long tid = syscall(__NR_gettid);
unsigned long tid = syscall(__NR_gettid);
#endif
snprintf(path, sizeof path, "%s/ug-%lu", get_temp_dir(), tid);
// snprintf(path, sizeof path, "%s/ug-%lu", get_temp_dir(), tid);
strncpy(path, get_temp_dir(), sizeof path);
path[sizeof path - 1] = '\0';
strncat(path + strlen(path), "/ug-bt-", sizeof path - strlen(path) - 1);
while (tid != 0 && strlen(path) < sizeof path - 1) {
// (tid will be actually printed in reversed order (123->321))
size_t len = strlen(path);
path[len] = '0' + tid % 10;
path[len + 1] = '\0';
tid /= 10;
}
int fd = open(path, O_CLOEXEC | O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
unlink(path);
#endif
@@ -1278,7 +1293,7 @@ print_stacktrace_glibc()
fd = STDERR_FILENO;
}
char backtrace_msg[] = "Backtrace:\n";
write_all(fd, sizeof backtrace_msg, backtrace_msg);
write_all(fd, sizeof backtrace_msg - 1, backtrace_msg);
array<void *, 256> addresses{};
const int num_symbols = backtrace(addresses.data(), addresses.size());
backtrace_symbols_fd(addresses.data(), num_symbols, fd);