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PrintStackTrace: don't symbolize if LLVM_DISABLE_SYMBOLIZATION is set

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See http://lists.llvm.org/pipermail/llvm-dev/2017-June/113975.html for a related previous discussion.
Many tools install signal handlers to print stack traces and optionally
symbolize the addresses with an external program 'llvm-symbolizer' (when
searching for 'llvm-symbolizer', the directory containg the executable
is preferred over PATH).

'llvm-symbolizer' can be slow if the executable is large and/or if
llvm-symbolizer' itself is under-optimized. For example, my 'llvm-lto2' from a
-DCMAKE_BUILD_TYPE=Debug build is 443MiB. The 'llvm-symbolizer' from the same
build takes ~2s to symbolize it. (An optimized 'llvm-symbolizer' takes 0.34s).
A crashed clang may take more than 5s to symbolize a stack trace.

If a test file has several `not --crash` RUN lines. It can be very slow in a Debug build.
This patch makes `not --crash` set an environment variable to suppress symbolization.
This is similar to D33804 which uses a command line option.
I pick 'symbolization' instead of 'symbolication' because the former is
used much more commonly and its stem matches 'llvm-symbolizer'.

Also set LLVM_DISABLE_CRASH_REPORT=1, which is currently only applicable on
`__APPLE__`.

Reviewed By: dblaikie, aganea

Differential Revision: https://reviews.llvm.org/D86170
This commit is contained in:
Fangrui Song 2020-08-20 08:14:10 -07:00
parent 5585c57018
commit d531bf5b5c
3 changed files with 22 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
lib/Support/Signals.cpp
View File

@ -44,6 +44,8 @@ static cl::opt<bool, true>
cl::desc("Disable symbolizing crash backtraces."),
cl::location(DisableSymbolicationFlag), cl::Hidden);
constexpr char DisableSymbolizationEnv[] = "LLVM_DISABLE_SYMBOLIZATION";
// Callbacks to run in signal handler must be lock-free because a signal handler
// could be running as we add new callbacks. We don't add unbounded numbers of
// callbacks, an array is therefore sufficient.
@ -105,7 +107,7 @@ static FormattedNumber format_ptr(void *PC) {
LLVM_ATTRIBUTE_USED
static bool printSymbolizedStackTrace(StringRef Argv0, void **StackTrace,
int Depth, llvm::raw_ostream &OS) {
if (DisableSymbolicationFlag)
if (DisableSymbolicationFlag || getenv(DisableSymbolizationEnv))
return false;
// Don't recursively invoke the llvm-symbolizer binary.

5
test/tools/not/disable-symbolization.test Normal file
View File

@ -0,0 +1,5 @@
# RUN: not --crash printenv > %t || true
# RUN: FileCheck %s < %t
# CHECK-DAG: LLVM_DISABLE_CRASH_REPORT=1
# CHECK-DAG: LLVM_DISABLE_SYMBOLIZATION=1

14
utils/not/not.cpp
View File

@ -15,6 +15,10 @@
#include "llvm/Support/WithColor.h"
#include "llvm/Support/raw_ostream.h"
#ifdef _WIN32
#include <windows.h>
#endif
using namespace llvm;
int main(int argc, const char **argv) {
@ -27,6 +31,16 @@ int main(int argc, const char **argv) {
++argv;
--argc;
ExpectCrash = true;
// Crash is expected, so disable crash report and symbolization to reduce
// output and avoid potentially slow symbolization.
#ifdef _WIN32
SetEnvironmentVariableA("LLVM_DISABLE_CRASH_REPORT", "1");
SetEnvironmentVariableA("LLVM_DISABLE_SYMBOLIZATION", "1");
#else
setenv("LLVM_DISABLE_CRASH_REPORT", "1", 0);
setenv("LLVM_DISABLE_SYMBOLIZATION", "1", 0);
#endif
}
if (argc == 0)