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It is not safe to call fork in PrintStackTrace. Sometimes it freezes the program.

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llvm-svn: 47161
This commit is contained in:
Lauro Ramos Venancio 2008-02-15 18:05:54 +00:00
parent e34f24132b
commit 4fcf9513f1
1 changed files with 2 additions and 44 deletions
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46
lib/System/Unix/Signals.inc
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@ -61,54 +61,12 @@ void* StackTrace[256];
// trace so that the user has an indication of why and where we died.
//
// On glibc systems we have the 'backtrace' function, which works nicely, but
// doesn't demangle symbols. In order to backtrace symbols, we fork and exec a
// 'c++filt' process to do the demangling. This seems like the simplest and
// most robust solution when we can't allocate memory (such as in a signal
// handler). If we can't find 'c++filt', we fallback to printing mangled names.
//
// doesn't demangle symbols.
void PrintStackTrace() {
#ifdef HAVE_BACKTRACE
// Use backtrace() to output a backtrace on Linux systems with glibc.
int depth = backtrace(StackTrace, array_lengthof(StackTrace));
// Create a one-way unix pipe. The backtracing process writes to PipeFDs[1],
// the c++filt process reads from PipeFDs[0].
int PipeFDs[2];
if (pipe(PipeFDs)) {
backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
return;
}
switch (pid_t ChildPID = fork()) {
case -1: // Error forking, print mangled stack trace
close(PipeFDs[0]);
close(PipeFDs[1]);
backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
return;
default: // backtracing process
close(PipeFDs[0]); // Close the reader side.
// Print the mangled backtrace into the pipe.
backtrace_symbols_fd(StackTrace, depth, PipeFDs[1]);
close(PipeFDs[1]); // We are done writing.
while (waitpid(ChildPID, 0, 0) == -1)
if (errno != EINTR) break;
return;
case 0: // c++filt process
close(PipeFDs[1]); // Close the writer side.
dup2(PipeFDs[0], 0); // Read from standard input
close(PipeFDs[0]); // Close the old descriptor
dup2(2, 1); // Revector stdout -> stderr
// Try to run c++filt or gc++filt. If neither is found, call back on 'cat'
// to print the mangled stack trace. If we can't find cat, just exit.
execlp("c++filt", "c++filt", (char*)NULL);
execlp("gc++filt", "gc++filt", (char*)NULL);
execlp("cat", "cat", (char*)NULL);
execlp("/bin/cat", "cat", (char*)NULL);
exit(0);
}
backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
#endif
}