r327863 - [Driver] Avoid invalidated iterator in insertTargetAndModeArgs

[Serge Pavlov via cfe-commits]

Author: sepavloff
Date: Mon Mar 19 09:13:43 2018
New Revision: 327863

URL: http://llvm.org/viewvc/llvm-project?rev=327863&view=rev
Log:
[Driver] Avoid invalidated iterator in insertTargetAndModeArgs

Doing an .insert() can potentially invalidate iterators by reallocating the
vector's storage. When all the stars align just right, this causes segfaults
or glibc aborts.

Gentoo Linux bug (crashes while building Chromium): https://bugs.gentoo.org/650082.

Patch by Hector Martin!

Differential Revision: https://reviews.llvm.org/D44607

Modified:
    cfe/trunk/tools/driver/driver.cpp

Modified: cfe/trunk/tools/driver/driver.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/tools/driver/driver.cpp?rev=327863&r1=327862&r2=327863&view=diff
==============================================================================
--- cfe/trunk/tools/driver/driver.cpp (original)
+++ cfe/trunk/tools/driver/driver.cpp Mon Mar 19 09:13:43 2018
@@ -212,20 +212,21 @@ static void insertTargetAndModeArgs(cons
   // Put target and mode arguments at the start of argument list so that
   // arguments specified in command line could override them. Avoid putting
   // them at index 0, as an option like '-cc1' must remain the first.
-  auto InsertionPoint = ArgVector.begin();
-  if (InsertionPoint != ArgVector.end())
+  int InsertionPoint = 0;
+  if (ArgVector.size() > 0)
     ++InsertionPoint;
 
   if (NameParts.DriverMode) {
     // Add the mode flag to the arguments.
-    ArgVector.insert(InsertionPoint,
+    ArgVector.insert(ArgVector.begin() + InsertionPoint,
                      GetStableCStr(SavedStrings, NameParts.DriverMode));
   }
 
   if (NameParts.TargetIsValid) {
     const char *arr[] = {"-target", GetStableCStr(SavedStrings,
                                                   NameParts.TargetPrefix)};
-    ArgVector.insert(InsertionPoint, std::begin(arr), std::end(arr));
+    ArgVector.insert(ArgVector.begin() + InsertionPoint,
+                     std::begin(arr), std::end(arr));
   }
 }