Fix PR1820, an incredibly subtle macro expansion bug that Neil discovered.
Neil, please review this fix.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@44285 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Lex/Preprocessor.cpp b/Lex/Preprocessor.cpp
index 0970590..a685b0b 100644
--- a/Lex/Preprocessor.cpp
+++ b/Lex/Preprocessor.cpp
@@ -941,6 +941,16 @@
// If this is a comment token in the argument list and we're just in
// -C mode (not -CC mode), discard the comment.
continue;
+ } else if (Tok.is(tok::identifier)) {
+ // Reading macro arguments can cause macros that we are currently
+ // expanding from to be popped off the expansion stack. Doing so causes
+ // them to be reenabled for expansion. Here we record whether any
+ // identifiers we lex as macro arguments correspond to disabled macros.
+ // If so, we mark the token as noexpand. This is a subtle aspect of
+ // C99 6.10.3.4p2.
+ if (MacroInfo *MI = getMacroInfo(Tok.getIdentifierInfo()))
+ if (!MI->isEnabled())
+ Tok.setFlag(Token::DisableExpand);
}
ArgTokens.push_back(Tok);
diff --git a/test/Preprocessor/macro_disable4.c b/test/Preprocessor/macro_disable4.c
new file mode 100644
index 0000000..4858813
--- /dev/null
+++ b/test/Preprocessor/macro_disable4.c
@@ -0,0 +1,6 @@
+// RUN: clang -P -E %s | grep 'int f(void)'
+// PR1820
+
+#define f(x) h(x
+#define h(x) x(void)
+extern int f(f));