Allow empty statements in naked functions in addition to ASM statements

[• ehsan]

Summary

This fixes PR20883.

[hans]

lib/Sema/SemaDecl.cpp

10429

Hmm, it feels like there could be other statements which don't have any children but are not a NullStmt. Might be safer to just check for NullStmt explicitly.

[• ehsan]

Addressed the review comment.

[hans]

LGTM, thanks for fixing!

test/Sema/attr-naked.c

27

Maybe add a t7 that has the actual case from the PR, i.e. both an asm and null statement.

[• ehsan]

Closed by commit rL217413 (authored by @ehsan).

lib/Sema/SemaDecl.cpp

if (Body) {
 
     if (!IsInstantiation && FD && FD->isConstexpr() && !FD->isInvalidDecl() &&
         (!CheckConstexprFunctionDecl(FD) ||
          !CheckConstexprFunctionBody(FD, Body)))
       FD->setInvalidDecl();
 
     if (FD && FD->hasAttr<NakedAttr>()) {
       for (const Stmt *S : Body->children()) {
-        if (!isa<AsmStmt>(S)) {
+        if (!isa<AsmStmt>(S) && S->child_begin() != S->child_end()) {
           Diag(S->getLocStart(), diag::err_non_asm_stmt_in_naked_function);
           Diag(FD->getAttr<NakedAttr>()->getLocation(), diag::note_attribute);
           FD->setInvalidDecl();
           break;
         }
       }
     }
 

test/Sema/attr-naked.c

__attribute__((naked)) int t4() {
   asm("movl $42, %eax");
   asm("retl");
 }
 
 __attribute__((naked)) int t5(int x) {
   asm("movl x, %eax");
   asm("retl");
 }
+
+__attribute__((naked)) void t6() {
+  ;
+}