Remove unnecessary in C++11 c_str() calls (microsoft#5932)

While theoratically required in pre-C++11 to avoid re-allocation upon
call, C++11 guarantees that c_str() returns a pointer to the internal
array so pre-calling c_str() is no longer required.

llvm-svn: 242983

---------

Co-authored-by: Yaron Keren <[email protected]>

Author: bob80905

lib/Support/Unix/Signals.inc

@@ -144,9 +144,6 @@ static void RemoveFilesToRemove() {
   // memory.
   std::vector<std::string>& FilesToRemoveRef = *FilesToRemove;
   for (unsigned i = 0, e = FilesToRemoveRef.size(); i != e; ++i) {
-    // We rely on a std::string implementation for which repeated calls to
-    // 'c_str()' don't allocate memory. We pre-call 'c_str()' on all of these
-    // strings to try to ensure this is safe.
     const char *path = FilesToRemoveRef[i].c_str();
 
     // Get the status so we can determine if it's a file or directory. If we
@@ -235,21 +232,7 @@ bool llvm::sys::RemoveFileOnSignal(StringRef Filename,
                                    std::string* ErrMsg) {
   {
     sys::SmartScopedLock<true> Guard(*SignalsMutex);
-    std::vector<std::string>& FilesToRemoveRef = *FilesToRemove;
-    std::string *OldPtr =
-        FilesToRemoveRef.empty() ? nullptr : &FilesToRemoveRef[0];
-    FilesToRemoveRef.push_back(Filename);
-
-    // We want to call 'c_str()' on every std::string in this vector so that if
-    // the underlying implementation requires a re-allocation, it happens here
-    // rather than inside of the signal handler. If we see the vector grow, we
-    // have to call it on every entry. If it remains in place, we only need to
-    // call it on the latest one.
-    if (OldPtr == &FilesToRemoveRef[0])
-      FilesToRemoveRef.back().c_str();
-    else
-      for (unsigned i = 0, e = FilesToRemoveRef.size(); i != e; ++i)
-        FilesToRemoveRef[i].c_str();
+    FilesToRemove->push_back(Filename);
   }
 
   RegisterHandlers();
@@ -270,7 +253,7 @@ void llvm::sys::DontRemoveFileOnSignal(StringRef Filename) {
   // requires a reallocation on the first call may have had the call to c_str()
   // made on insertion become invalid by being copied down an element.
   for (std::vector<std::string>::iterator E = FilesToRemove->end(); I != E; ++I)
-    I->c_str();
+    (void)I->c_str();
 }
 
 /// AddSignalHandler - Add a function to be called when a signal is delivered