Allow empty assembly string literal with -fno-gnu-inline-asm

Empty assembly string will not introduce assembly code in the output
binary and it is often used as a trick in the header to disable
optimizations. It doesn't conflict with the purpose of the option so it
is allowed with -fno-gnu-inline-asm flag.

llvm-svn: 237073

1 files changed, 9 insertions, 4 deletions

diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
index ed27a9e3953..697fda9215d 100644
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -670,12 +670,17 @@ Parser::ParseExternalDeclaration(ParsedAttributesWithRange &attrs,
     SourceLocation StartLoc = Tok.getLocation();
     SourceLocation EndLoc;
 
-    // Check if GNU-style InlineAsm is disabled.
-    if (!getLangOpts().GNUAsm)
-      Diag(StartLoc, diag::err_gnu_inline_asm_disabled);
-
     ExprResult Result(ParseSimpleAsm(&EndLoc));
 
+    // Check if GNU-style InlineAsm is disabled.
+    // Empty asm string is allowed because it will not introduce
+    // any assembly code.
+    if (!(getLangOpts().GNUAsm || Result.isInvalid())) {
+      const auto *SL = cast<StringLiteral>(Result.get());
+      if (!SL->getString().trim().empty())
+        Diag(StartLoc, diag::err_gnu_inline_asm_disabled);
+    }
+
     ExpectAndConsume(tok::semi, diag::err_expected_after,
                      "top-level asm block");