From 1efdec2c252d1f64092fcf2d829b60171623cd74 Mon Sep 17 00:00:00 2001 From: Sjoerd Meijer Date: Mon, 17 Aug 2015 11:38:35 +0100 Subject: [PATCH] Always trap for missing return statements, except when optimizing for size. --- lib/CodeGen/CodeGenFunction.cpp | 7 ++++++- test/CodeGenCXX/return.cpp | 7 ++++--- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp index 9bf4161..a663f16 100644 --- a/lib/CodeGen/CodeGenFunction.cpp +++ b/lib/CodeGen/CodeGenFunction.cpp @@ -926,7 +926,12 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn, EmitCheck(std::make_pair(IsFalse, SanitizerKind::Return), "missing_return", EmitCheckSourceLocation(FD->getLocation()), None); - } else if (CGM.getCodeGenOpts().OptimizationLevel == 0) { + } else if (!CGM.getCodeGenOpts().OptimizeSize) { + // A missing return statement provides opportunities for optimizing away + // unreachable control flow, i.e it is a code-size optimization opportunity. + // However, not returning from a function is potentially unsafe and also not + // so user-friendly. Therefore, we trap for all optimizations levels, except + // when optimizing for size. EmitTrapCall(llvm::Intrinsic::trap); } Builder.CreateUnreachable(); diff --git a/test/CodeGenCXX/return.cpp b/test/CodeGenCXX/return.cpp index 5c1cfda..b02b2a8 100644 --- a/test/CodeGenCXX/return.cpp +++ b/test/CodeGenCXX/return.cpp @@ -1,5 +1,6 @@ // RUN: %clang_cc1 -emit-llvm -triple %itanium_abi_triple -o - %s | FileCheck %s -// RUN: %clang_cc1 -emit-llvm -triple %itanium_abi_triple -O -o - %s | FileCheck %s --check-prefix=CHECK-OPT +// RUN: %clang_cc1 -emit-llvm -triple %itanium_abi_triple -O -o - %s | FileCheck %s +// RUN: %clang_cc1 -emit-llvm -triple %itanium_abi_triple -Oz -o - %s | FileCheck %s --check-prefix=CHECK-OPT-SIZE // CHECK: @_Z9no_return // CHECK-OPT: @_Z9no_return @@ -7,6 +8,6 @@ int no_return() { // CHECK: call void @llvm.trap // CHECK-NEXT: unreachable - // CHECK-OPT-NOT: call void @llvm.trap - // CHECK-OPT: unreachable + // CHECK-OPT-SIZE-NOT: call void @llvm.trap + // CHECK-OPT-SIZE: unreachable } -- 1.9.1