Use libdl to get symbols for backtraces

With this patch, it'll look like this:

$ out/x64.optdebug/d8 --expose-trigger-failure test/mjsunit/mjsunit.js test/mjsunit/verify-assert-false.js

==== C stack trace ===============================

 1: V8_Fatal
 2: v8::internal::FunctionCallbackArguments::Call(void (*)(v8::FunctionCallbackInfo<v8::Value> const&))
 3: 0x727ced
 4: 0x72b6ba
 5: 0x188c7f607f9b

BUG=none
R=svenpanne@chromium.org
LOG=y

Review URL: https://codereview.chromium.org/1018313003

Cr-Commit-Position: refs/heads/master@{#27318}

BUILD.gn

@@ -1393,7 +1393,7 @@ source_set("v8_libbase") {
   if (is_linux) {
     sources += [ "src/base/platform/platform-linux.cc" ]
 
-    libs = [ "rt" ]
+    libs = [ "dl", "rt" ]
   } else if (is_android) {
     defines += [ "CAN_USE_VFP_INSTRUCTIONS" ]
 

src/base/logging.cc

@@ -5,10 +5,11 @@
 #include "src/base/logging.h"
 
 #if V8_LIBC_GLIBC || V8_OS_BSD
-# include <cxxabi.h>
-# include <execinfo.h>
+#include <cxxabi.h>
+#include <dlfcn.h>
+#include <execinfo.h>
 #elif V8_OS_QNX
-# include <backtrace.h>
+#include <backtrace.h>
 #endif  // V8_LIBC_GLIBC || V8_OS_BSD
 
 #include <cstdio>
@@ -54,28 +55,24 @@ void DumpBacktrace() {
 #if V8_LIBC_GLIBC || V8_OS_BSD
   void* trace[100];
   int size = backtrace(trace, arraysize(trace));
-  char** symbols = backtrace_symbols(trace, size);
   OS::PrintError("\n==== C stack trace ===============================\n\n");
   if (size == 0) {
     OS::PrintError("(empty)\n");
-  } else if (symbols == NULL) {
-    OS::PrintError("(no symbols)\n");
   } else {
     for (int i = 1; i < size; ++i) {
       OS::PrintError("%2d: ", i);
-      char mangled[201];
-      if (sscanf(symbols[i], "%*[^(]%*[(]%200[^)+]", mangled) == 1) {  // NOLINT
-        int status;
-        size_t length;
-        char* demangled = abi::__cxa_demangle(mangled, NULL, &length, &status);
-        OS::PrintError("%s\n", demangled != NULL ? demangled : mangled);
+      Dl_info info;
+      char* demangled = NULL;
+      if (!dladdr(trace[i], &info) || !info.dli_sname) {
+        OS::PrintError("%p\n", trace[i]);
+      } else if ((demangled = abi::__cxa_demangle(info.dli_sname, 0, 0, 0))) {
+        OS::PrintError("%s\n", demangled);
         free(demangled);
       } else {
-        OS::PrintError("??\n");
+        OS::PrintError("%s\n", info.dli_sname);
       }
     }
   }
-  free(symbols);
 #elif V8_OS_QNX
   char out[1024];
   bt_accessor_t acc;

tools/gyp/v8.gyp

@@ -1370,6 +1370,7 @@
               ['nacl_target_arch=="none"', {
                 'link_settings': {
                   'libraries': [
+                    '-ldl',
                     '-lrt'
                   ],
                 },
@@ -1389,6 +1390,11 @@
             'sources': [
               '../../src/base/platform/platform-posix.cc'
             ],
+            'link_settings': {
+              'libraries': [
+                '-ldl'
+              ]
+            },
             'conditions': [
               ['host_os=="mac"', {
                 'target_conditions': [