[llvm] r269992 - Work around a glibc bug: backtrace() spuriously fails if
Richard Smith via llvm-commits
llvm-commits at lists.llvm.org
Wed May 18 15:26:36 PDT 2016
Author: rsmith
Date: Wed May 18 17:26:36 2016
New Revision: 269992
URL: http://llvm.org/viewvc/llvm-project?rev=269992&view=rev
Log:
Work around a glibc bug: backtrace() spuriously fails if
- glibc is dynamically linked, and
- libgcc_s is unavailable (for instance, another library is being used to
provide the compiler runtime or libgcc is statically linked), and
- the target is x86_64.
If we run backtrace() and it fails to find any stack frames, try using
_Unwind_Backtrace instead if available.
Modified:
llvm/trunk/cmake/config-ix.cmake
llvm/trunk/lib/Support/Unix/Signals.inc
Modified: llvm/trunk/cmake/config-ix.cmake
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/cmake/config-ix.cmake?rev=269992&r1=269991&r2=269992&view=diff
==============================================================================
--- llvm/trunk/cmake/config-ix.cmake (original)
+++ llvm/trunk/cmake/config-ix.cmake Wed May 18 17:26:36 2016
@@ -144,6 +144,7 @@ endif()
# function checks
check_symbol_exists(arc4random "stdlib.h" HAVE_DECL_ARC4RANDOM)
check_symbol_exists(backtrace "execinfo.h" HAVE_BACKTRACE)
+check_symbol_exists(_Unwind_Backtrace "unwind.h" HAVE_UNWIND_BACKTRACE)
check_symbol_exists(getpagesize unistd.h HAVE_GETPAGESIZE)
check_symbol_exists(getrusage sys/resource.h HAVE_GETRUSAGE)
check_symbol_exists(setrlimit sys/resource.h HAVE_SETRLIMIT)
Modified: llvm/trunk/lib/Support/Unix/Signals.inc
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Unix/Signals.inc?rev=269992&r1=269991&r2=269992&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Unix/Signals.inc (original)
+++ llvm/trunk/lib/Support/Unix/Signals.inc Wed May 18 17:26:36 2016
@@ -45,6 +45,9 @@
#if HAVE_LINK_H
#include <link.h>
#endif
+#if HAVE_UNWIND_BACKTRACE
+#include <unwind.h>
+#endif
using namespace llvm;
@@ -309,17 +312,61 @@ static bool findModulesAndOffsets(void *
}
#endif // defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES) && ...
+#if defined(ENABLE_BACKTRACES) && defined(HAVE_UNWIND_BACKTRACE)
+static int unwindBacktrace(void **StackTrace, int MaxEntries) {
+ if (MaxEntries < 0)
+ return 0;
+
+ // Skip the first frame ('unwindBacktrace' itself).
+ int Entries = -1;
+
+ auto HandleFrame = [&](_Unwind_Context *Context) -> _Unwind_Reason_Code {
+ // Apparently we need to detect reaching the end of the stack ourselves.
+ void *IP = (void *)_Unwind_GetIP(Context);
+ if (!IP)
+ return _URC_END_OF_STACK;
+
+ assert(Entries < MaxEntries && "recursively called after END_OF_STACK?");
+ if (Entries >= 0)
+ StackTrace[Entries] = IP;
+
+ if (++Entries == MaxEntries)
+ return _URC_END_OF_STACK;
+ return _URC_NO_REASON;
+ };
+
+ _Unwind_Backtrace(
+ [](_Unwind_Context *Context, void *Handler) {
+ return (*static_cast<decltype(HandleFrame) *>(Handler))(Context);
+ },
+ static_cast<void *>(&HandleFrame));
+ return std::max(Entries, 0);
+}
+#endif
+
// PrintStackTrace - In the case of a program crash or fault, print out a stack
// 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.
void llvm::sys::PrintStackTrace(raw_ostream &OS) {
-#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
- static void* StackTrace[256];
+#if defined(ENABLE_BACKTRACES)
+ static void *StackTrace[256];
+ int depth = 0;
+#if defined(HAVE_BACKTRACE)
// Use backtrace() to output a backtrace on Linux systems with glibc.
- int depth = backtrace(StackTrace,
+ if (!depth)
+ depth = backtrace(StackTrace, static_cast<int>(array_lengthof(StackTrace)));
+#endif
+#if defined(HAVE_UNWIND_BACKTRACE)
+ // Try _Unwind_Backtrace() if backtrace() failed.
+ if (!depth)
+ depth = unwindBacktrace(StackTrace,
static_cast<int>(array_lengthof(StackTrace)));
+#endif
+ if (!depth)
+ return;
+
if (printSymbolizedStackTrace(StackTrace, depth, OS))
return;
#if HAVE_DLFCN_H && __GNUG__
@@ -369,7 +416,7 @@ void llvm::sys::PrintStackTrace(raw_ostr
}
OS << '\n';
}
-#else
+#elif defined(HAVE_BACKTRACE)
backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
#endif
#endif
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