[gcc r12-3145] Fix PR c++/66590: incorrect warning "reaches end of non-void function" for switch

[gcc r12-3145] Fix PR c++/66590: incorrect warning "reaches end of non-void function" for switch

[Andrew Pinski]

https://gcc.gnu.org/g:971df602e0a798fe9c805c3105f4ac80d638a12b

commit r12-3145-g971df602e0a798fe9c805c3105f4ac80d638a12b
Author: Andrew Pinski <apinski@marvell.com>
Date:   Mon Aug 9 18:33:17 2021 -0700

    Fix PR c++/66590: incorrect warning "reaches end of non-void function" for switch
    
    So the problem here is there is code in the C++ front-end not to add a
    break statement (to the IR) if the previous block does not fall through.
    The problem is the code which does the check to see if the block
    may fallthrough does not check a CLEANUP_STMT; it assumes it is always
    fall through.  Anyways this adds the code for the case of a CLEANUP_STMT
    that is only for !CLEANUP_EH_ONLY (the try/finally case).
    
    OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.
    
    gcc/cp/ChangeLog:
    
            PR c++/66590
            * cp-objcp-common.c (cxx_block_may_fallthru): Handle
            CLEANUP_STMT for the case which will be try/finally.
    
    gcc/testsuite/ChangeLog:
    
            PR c++/66590
            * g++.dg/warn/Wreturn-5.C: New test.

Diff:
---
 gcc/cp/cp-objcp-common.c              |  9 +++++++++
 gcc/testsuite/g++.dg/warn/Wreturn-5.C | 15 +++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/gcc/cp/cp-objcp-common.c b/gcc/cp/cp-objcp-common.c
index 98fd96227c4..28f2d7bee71 100644
--- a/gcc/cp/cp-objcp-common.c
+++ b/gcc/cp/cp-objcp-common.c
@@ -317,6 +317,15 @@ cxx_block_may_fallthru (const_tree stmt)
 	return true;
       return block_may_fallthru (ELSE_CLAUSE (stmt));
 
+    case CLEANUP_STMT:
+      /* Just handle the try/finally cases.  */
+      if (!CLEANUP_EH_ONLY (stmt))
+	{
+	  return (block_may_fallthru (CLEANUP_BODY (stmt))
+		  && block_may_fallthru (CLEANUP_EXPR (stmt)));
+	}
+      return true;
+
     default:
       return c_block_may_fallthru (stmt);
     }
diff --git a/gcc/testsuite/g++.dg/warn/Wreturn-5.C b/gcc/testsuite/g++.dg/warn/Wreturn-5.C
new file mode 100644
index 00000000000..543e33e905d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wreturn-5.C
@@ -0,0 +1,15 @@
+// PR C++/66590
+// { dg-do compile }
+// { dg-options "-Wall" }
+
+struct A{ ~A();};
+
+int f(int x)
+{
+    A a;
+    switch (x)
+    {
+        case 1: { A tmp; return 1; } break;
+        default: return 0;
+    }
+}	// { dg-bogus "control reaches end of non-void function" }