From 06cad825cdd4c819e88eac8179a06d196304e78e Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Thu, 20 Aug 2020 08:14:10 -0700 Subject: [PATCH] PrintStackTrace: don't symbolize if LLVM_DISABLE_SYMBOLIZATION is set 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 --- llvm/lib/Support/Signals.cpp | 4 +++- llvm/test/tools/not/disable-symbolization.test | 5 +++++ llvm/utils/not/not.cpp | 14 ++++++++++++++ 3 files changed, 22 insertions(+), 1 deletion(-) create mode 100644 llvm/test/tools/not/disable-symbolization.test diff --git a/llvm/lib/Support/Signals.cpp b/llvm/lib/Support/Signals.cpp index 2cfdf2d42a4a..83a606b59df3 100644 --- a/llvm/lib/Support/Signals.cpp +++ b/llvm/lib/Support/Signals.cpp @@ -44,6 +44,8 @@ static cl::opt 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. diff --git a/llvm/test/tools/not/disable-symbolization.test b/llvm/test/tools/not/disable-symbolization.test new file mode 100644 index 000000000000..05dbf9db053e --- /dev/null +++ b/llvm/test/tools/not/disable-symbolization.test @@ -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 diff --git a/llvm/utils/not/not.cpp b/llvm/utils/not/not.cpp index f00b9c8dde42..4454035b079e 100644 --- a/llvm/utils/not/not.cpp +++ b/llvm/utils/not/not.cpp @@ -15,6 +15,10 @@ #include "llvm/Support/WithColor.h" #include "llvm/Support/raw_ostream.h" +#ifdef _WIN32 +#include +#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)