r191382 - PR17359: Fix off-by-one OOB on _Pragma("") and an unescaping bug

[Reid Kleckner]

Author: rnk
Date: Wed Sep 25 11:42:48 2013
New Revision: 191382

URL: http://llvm.org/viewvc/llvm-project?rev=191382&view=rev
Log:
PR17359: Fix off-by-one OOB on _Pragma("") and an unescaping bug

Previously the code would reduce a run of backslashes to a single
backslash, and now it will properly leave behind every other backslash.

Modified:
    cfe/trunk/lib/Lex/Pragma.cpp
    cfe/trunk/test/Preprocessor/_Pragma.c

Modified: cfe/trunk/lib/Lex/Pragma.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Lex/Pragma.cpp?rev=191382&r1=191381&r2=191382&view=diff
==============================================================================
--- cfe/trunk/lib/Lex/Pragma.cpp (original)
+++ cfe/trunk/lib/Lex/Pragma.cpp Wed Sep 25 11:42:48 2013
@@ -263,14 +263,14 @@ void Preprocessor::Handle_Pragma(Token &
 
     // Remove escaped quotes and escapes.
     unsigned ResultPos = 1;
-    for (unsigned i = 1, e = StrVal.size() - 2; i != e; ++i) {
-      if (StrVal[i] != '\\' ||
-          (StrVal[i + 1] != '\\' && StrVal[i + 1] != '"')) {
-        // \\ -> '\' and \" -> '"'.
-        StrVal[ResultPos++] = StrVal[i];
-      }
+    for (unsigned i = 1, e = StrVal.size() - 1; i != e; ++i) {
+      // Skip escapes.  \\ -> '\' and \" -> '"'.
+      if (StrVal[i] == '\\' && i + 1 < e &&
+          (StrVal[i + 1] == '\\' || StrVal[i + 1] == '"'))
+        ++i;
+      StrVal[ResultPos++] = StrVal[i];
     }
-    StrVal.erase(StrVal.begin() + ResultPos, StrVal.end() - 2);
+    StrVal.erase(StrVal.begin() + ResultPos, StrVal.end() - 1);
   }
 
   // Remove the front quote, replacing it with a space, so that the pragma

Modified: cfe/trunk/test/Preprocessor/_Pragma.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Preprocessor/_Pragma.c?rev=191382&r1=191381&r2=191382&view=diff
==============================================================================
--- cfe/trunk/test/Preprocessor/_Pragma.c (original)
+++ cfe/trunk/test/Preprocessor/_Pragma.c Wed Sep 25 11:42:48 2013
@@ -5,6 +5,9 @@ _Pragma ("GCC system_header")  // expect
 // rdar://6880630
 _Pragma("#define macro")    // expected-warning {{unknown pragma ignored}}
 
+_Pragma("") // expected-warning {{unknown pragma ignored}}
+_Pragma("message(\"foo \\\\\\\\ bar\")") // expected-warning {{foo \\ bar}}
+
 #ifdef macro
 #error #define invalid
 #endif