Use file offsets in traces if object has no symbols

CMakeLists.txt

@@ -22,7 +22,7 @@ option (WITH_THREADS "Enable multithreading support" ON)
 option (WITH_TLS "Enable Thread Local Storage (TLS) support" ON)
 option (BUILD_SHARED_LIBS "Build shared libraries" OFF)
 option (PRINT_UNSYMBOLIZED_STACK_TRACES
-  "Print raw pc values on symbolization failure" OFF)
+  "Print file offsets in traces instead of symbolizing" OFF)
 option (WITH_PKGCONFIG "Enable pkg-config support" ON)
 option (WITH_UNWIND "Enable libunwind support" ON)
 

configure.ac

@@ -209,11 +209,11 @@ AC_DEFINE_UNQUOTED(TEST_SRC_DIR, "$srcdir", [location of source code])
 
 AC_ARG_ENABLE(unsymbolized-traces,
               AS_HELP_STRING([--enable-unsymbolized-traces],
-                             [Print raw pc values when symbolization is failed.]),
+                             [Print file offsets in traces instead of symbolizing.]),
               enable_unsymbolized_traces=yes)
 if test x"$enable_unsymbolized_traces" = x"yes"; then
   AC_DEFINE(PRINT_UNSYMBOLIZED_STACK_TRACES, 1,
-            [define if we should print raw pc values on symbolization failure.])
+            [define if we should print file offsets in traces instead of symbolizing.])
 fi
 
 # These are what's needed by logging.h.in and raw_logging.h.in

src/config.h.cmake.in

@@ -170,7 +170,7 @@
 /* How to access the PC from a struct ucontext */
 #cmakedefine PC_FROM_UCONTEXT
 
-/* define if we should print raw pc values on symbolization failure. */
+/* define if we should print file offsets in traces instead of symbolizing. */
 #cmakedefine PRINT_UNSYMBOLIZED_STACK_TRACES
 
 /* Define to necessary symbol if this constant uses a non-standard name on

src/symbolize.cc

@@ -312,6 +312,7 @@ FindSymbol(uint64_t pc, const int fd, char *out, int out_size,
         ssize_t len1 = ReadFromOffset(fd, out, out_size,
                                       strtab->sh_offset + symbol.st_name);
         if (len1 <= 0 || memchr(out, '\0', out_size) == NULL) {
+          memset(out, 0, out_size);
           return false;
         }
         return true;  // Obtained the symbol name.
@@ -783,9 +784,10 @@ static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
                                                              out_size - 1);
   }
 
+  FileDescriptor wrapped_object_fd(object_fd);
+
 #if defined(PRINT_UNSYMBOLIZED_STACK_TRACES)
   {
-    FileDescriptor wrapped_object_fd(object_fd);
 #else
   // Check whether a file name was returned.
   if (object_fd < 0) {
@@ -804,7 +806,6 @@ static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
     // Failed to determine the object file containing PC.  Bail out.
     return false;
   }
-  FileDescriptor wrapped_object_fd(object_fd);
   int elf_type = FileGetElfType(wrapped_object_fd.get());
   if (elf_type == -1) {
     return false;
@@ -824,6 +825,17 @@ static ATTRIBUTE_NOINLINE bool SymbolizeAndDemangle(void *pc, char *out,
   }
   if (!GetSymbolFromObjectFile(wrapped_object_fd.get(), pc0,
                                out, out_size, base_address)) {
+    if (out[1] && !g_symbolize_callback) {
+      // The object file containing PC was opened successfully however the
+      // symbol was not found. The object may have been stripped. This is still
+      // considered success because the object file name and offset are known
+      // and tools like asan_symbolize.py can be used for the symbolization.
+      out[out_size - 1] = '\0';  // Making sure |out| is always null-terminated.
+      SafeAppendString("+0x", out, out_size);
+      SafeAppendHexNumber(pc0 - base_address, out, out_size);
+      SafeAppendString(")", out, out_size);
+      return true;
+    }
     return false;
   }