Clang fails to add uwtable to some functions

[llvmbot]

Bugzilla Link	19213
Version	unspecified
OS	All
Reporter	LLVM Bugzilla Contributor
CC	@dwblaikie,@DougGregor

Extended Description

When compiling

int f1();
int i = f1();

clang fails to add uwtable to _GLOBAL__I_a. This means that when building without exceptions, we don't add an entry for it in .eh_table, which violates the ABI.

GCC produces one:

	.type	_GLOBAL__sub_I_i, @function
_GLOBAL__sub_I_i:
.LFB1:
	.cfi_startproc
....

[dwblaikie]

Most of Clang's codegen uses CodeGenModule::SetLLVMFunctionAttributesForDefinition which (correctly?) sets UWTable based on CodeGenOpts.UnwindTables.

Global ctors/dtors use CGDeclCXX.cpp:CreateGlobalInitOrDestructFunction which doesn't handle UWTable (and looks like it doesn't adequately check for nounwind - it just checks LangOpts.Exceptions, whereas CodeGenModule uses CodeGenModule.cpp:hasUnwindExceptions, which checks LangOpts.Exceptions, LangOpts.CXXEcxeptions, and LangOpts.ObjCExceptions)

We should probably factor out the common parts of SetLLVMFunctionAttributesForDefinition (the ones that don't actually rely on the Clang AST Decl object) and reuse them from CreateGlobalInitOrDetsructFunction.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: None (llvmbot)

| | | | --- | --- | | Bugzilla Link | [19213](https://llvm.org/bz19213) | | Version | unspecified | | OS | All | | Reporter | LLVM Bugzilla Contributor | | CC | @dwblaikie,@DougGregor |

Extended Description

When compiling

int f1();
int i = f1();

clang fails to add uwtable to _GLOBAL__I_a. This means that when building without exceptions, we don't add an entry for it in .eh_table, which violates the ABI.

GCC produces one:

	.type	_GLOBAL__sub_I_i, @<!-- -->function
_GLOBAL__sub_I_i:
.LFB1:
	.cfi_startproc
....

[AaronBallman]

This appears to have been fixed in Clang 3.5: https://gcc.godbolt.org/z/fj7vPea9h If you're still seeing the issue, please reopen the issue with more details about how to reproduce.