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[CodeGen][CXX]: Fix no_destroy CG bug under specific circumstances 

Summary:

Class with no user-defined destructor that has an inherited member that has a
non-trivial destructor and a non-default constructor will attempt to emit a
destructor despite being marked as __attribute((no_destroy)) in which case it
would trigger an assertion due to an incorrect assumption. 

In addition this adds missing test coverage for IR generation for no_destroy.

(Note that here use of no_destroy is synonymous with its global flag 
counterpart `-fno-c++-static-destructors` being enabled)

Differential Revision: https://reviews.llvm.org/D54344

llvm-svn: 346628
This commit is contained in:
Kristina Brooks 2018-11-12 01:19:16 +00:00
parent 4f9b470029
commit 7349d90b74
2 changed files with 51 additions and 0 deletions
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9
clang/lib/CodeGen/CGDeclCXX.cpp
View File

@ -64,6 +64,15 @@ static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
/// static storage duration.
static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
ConstantAddress Addr) {
// Honor __attribute__((no_destroy)) and bail instead of attempting
// to emit a reference to a possibly nonexistent destructor, which
// in turn can cause a crash. This will result in a global constructor
// that isn't balanced out by a destructor call as intended by the
// attribute. This also checks for -fno-c++-static-destructors and
// bails even if the attribute is not present.
if (D.isNoDestroy(CGF.getContext()))
return;
CodeGenModule &CGM = CGF.CGM;
// FIXME: __attribute__((cleanup)) ?

42
clang/test/CodeGenCXX/attr-no-destroy-d54344.cpp Normal file
View File

@ -0,0 +1,42 @@
// RUN: %clang_cc1 -std=c++2a -emit-llvm -O0 -triple x86_64-unknown-linux-gnu -DNOATTR %s -o - | FileCheck %s
// RUN: %clang_cc1 -std=c++2a -emit-llvm -O0 -triple x86_64-unknown-linux-gnu %s -o - | FileCheck %s --check-prefix=CHECK-ATTR
// RUN: %clang_cc1 -std=c++2a -emit-llvm -O0 -triple x86_64-unknown-linux-gnu -DNOATTR -fno-c++-static-destructors %s -o - | FileCheck %s --check-prefix=CHECK-FLAG
// Regression test for D54344. Class with no user-defined destructor
// that has an inherited member that has a non-trivial destructor
// and a non-default constructor will attempt to emit a destructor
// despite being marked as __attribute((no_destroy)) in which case
// it would trigger an assertion due to an incorrect assumption.
// This test is more reliable with asserts to work as without
// the crash may (unlikely) could generate working but semantically
// incorrect code.
class a {
public:
~a();
};
class logger_base {
a d;
};
class e : logger_base {};
#ifndef NOATTR
__attribute((no_destroy))
#endif
e g;
// In the absence of the attribute and flag, both ctor and dtor should
// be emitted, check for that.
// CHECK: @__cxx_global_var_init
// CHECK: @__cxa_atexit
// When attribute is enabled, the constructor should not be balanced
// by a destructor. Make sure we have the ctor but not the dtor
// registration.
// CHECK-ATTR: @__cxx_global_var_init
// CHECK-ATTR-NOT: @__cxa_atexit
// Same scenario except with global flag (-fno-c++-static-destructors)
// supressing it instead of the attribute.
// CHECK-FLAG: @__cxx_global_var_init
// CHECK-FLAG-NOT: @__cxa_atexit