Don't warn on returning the address of a label from a statement expression

Summary:
There isn't anything inherently wrong with returning a label from a
statement expression. In practice, the Linux kernel uses this pattern to
materialize PCs.

Fixes PR38569

Reviewers: niravd, rsmith, nickdesaulniers

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D50805

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@340101 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index 766f23b05b006096d740ae69007e97116f9f6c93..1f28056e254f235469d4c2dbd1b77cf468cc1854 100644 (file)
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -6924,6 +6924,10 @@ void Sema::checkInitializerLifetime(const InitializedEntity &Entity,
       } else if (isa<BlockExpr>(L)) {
         Diag(DiagLoc, diag::err_ret_local_block) << DiagRange;
       } else if (isa<AddrLabelExpr>(L)) {
+        // Don't warn when returning a label from a statement expression.
+        // Leaving the scope doesn't end its lifetime.
+        if (LK == LK_StmtExprResult)
+          return false;
         Diag(DiagLoc, diag::warn_ret_addr_label) << DiagRange;
       } else {
         Diag(DiagLoc, diag::warn_ret_local_temp_addr_ref)

diff --git a/test/Sema/statements.c b/test/Sema/statements.c
index dbb4d56ee1d17aed11ba083e0f20b20cff1c4248..ddaec8d433efda01ab9fbfe53e584c7872f20809 100644 (file)
--- a/test/Sema/statements.c
+++ b/test/Sema/statements.c
@@ -34,6 +34,15 @@ bar:
   return &&bar;  // expected-warning {{returning address of label, which is local}}
 }
 
+// PR38569: Don't warn when returning a label from a statement expression.
+void test10_logpc(void*);
+void test10a() {
+  test10_logpc(({
+    my_pc:
+      &&my_pc;
+  }));
+}
+
 // PR6034
 void test11(int bit) {
   switch (bit)