Breakpad processor: Support negative literals in the postfix evaluator.

Some versions of the libstdc++, the GNU standard C++ library, have
stream extractors for unsigned integer values that permit a leading
'-' sign (6.0.13); others do not (6.0.9). Regardless of the behavior
of the extractors, Breakpad postfix expressions should support
negative literals.

a=jimblandy, r=nealsid


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@537 4c0a9323-5329-0410-9bdc-e9ce6186880e

1 files changed, 18 insertions, 4 deletions

diff --git a/src/processor/postfix_evaluator-inl.h b/src/processor/postfix_evaluator-inl.h
index 9c1fc84e..b1252f68 100644
--- a/src/processor/postfix_evaluator-inl.h
+++ b/src/processor/postfix_evaluator-inl.h
@@ -246,16 +246,30 @@ PostfixEvaluator<ValueType>::PopValueOrIdentifier(
   string token = stack_.back();
   stack_.pop_back();
 
-  // First, try to treat the value as a literal.  In order for this to
-  // succed, the entire string must be parseable as ValueType.  If this
-  // isn't possible, it can't be a literal, so treat it as an identifier
-  // instead.
+  // First, try to treat the value as a literal. Literals may have leading
+  // '-' sign, and the entire remaining string must be parseable as
+  // ValueType. If this isn't possible, it can't be a literal, so treat it
+  // as an identifier instead.
+  //
+  // Some versions of the libstdc++, the GNU standard C++ library, have
+  // stream extractors for unsigned integer values that permit a leading
+  // '-' sign (6.0.13); others do not (6.0.9). Since we require it, we
+  // handle it explicitly here.
   istringstream token_stream(token);
   ValueType literal;
+  bool negative;
+  if (token_stream.peek() == '-') {
+    negative = true;
+    token_stream.get();
+  } else {
+    negative = false;
+  }
   if (token_stream >> literal && token_stream.peek() == EOF) {
     if (value) {
       *value = literal;
     }
+    if (negative)
+      *value = -*value;
     return POP_RESULT_VALUE;
   } else {
     if (identifier) {