r223455 - Driver: Objective-C should respect -fno-exceptions
Nico Weber
thakis at chromium.org
Fri Dec 5 11:25:36 PST 2014
On Fri, Dec 5, 2014 at 12:56 AM, David Majnemer <david.majnemer at gmail.com>
wrote:
> Author: majnemer
> Date: Fri Dec 5 02:56:55 2014
> New Revision: 223455
>
> URL: http://llvm.org/viewvc/llvm-project?rev=223455&view=rev
> Log:
> Driver: Objective-C should respect -fno-exceptions
>
> Clang attempted to replicate a GCC bug: -fobjc-exceptions forces
> -fexceptions to be enabled. However, this has unintended effects and
> other awkard side effects that Clang doesn't "correctly" ape (e.g. it's
> impossible to turn off C++ exceptions in ObjC++ mode
What does "impossible to turn off exceptions" mean here?
$ clang -c test.mm -fno-exceptions
test.mm:2:3: error: cannot use 'try' with exceptions disabled
try {} catch (...) {}
^
1 error generated.
).
>
> Instead, -f[no]objc-exceptions and -f[no]cxx-exceptions now have an
> identical relationship with -f[no]exceptions.
>
Did anyone from Apple review this? I thought the intention was that
-fno-exceptions disables c++ exceptions but keeps objc exceptions enabled,
since a) many people don't want c++ exceptions so they use -fno-exceptions
but b) cocoa uses exceptions so you can't really build without objc
exceptions.
(I'm guessing I'm misunderstanding the patch somehow.)
>
> Added:
> cfe/trunk/test/Driver/exceptions.mm
> Removed:
> cfe/trunk/test/Driver/exceptions.m
> Modified:
> cfe/trunk/lib/Driver/Tools.cpp
> cfe/trunk/test/Driver/rewrite-legacy-objc.m
>
> Modified: cfe/trunk/lib/Driver/Tools.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/Tools.cpp?rev=223455&r1=223454&r2=223455&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/Driver/Tools.cpp (original)
> +++ cfe/trunk/lib/Driver/Tools.cpp Fri Dec 5 02:56:55 2014
> @@ -1894,23 +1894,6 @@ static void getTargetFeatures(const Driv
> }
> }
>
> -static bool
> -shouldUseExceptionTablesForObjCExceptions(const ObjCRuntime &runtime,
> - const llvm::Triple &Triple) {
> - // We use the zero-cost exception tables for Objective-C if the
> non-fragile
> - // ABI is enabled or when compiling for x86_64 and ARM on Snow Leopard
> and
> - // later.
> - if (runtime.isNonFragile())
> - return true;
> -
> - if (!Triple.isMacOSX())
> - return false;
> -
> - return (!Triple.isMacOSXVersionLT(10,5) &&
> - (Triple.getArch() == llvm::Triple::x86_64 ||
> - Triple.getArch() == llvm::Triple::arm));
> -}
> -
> // exceptionSettings() exists to share the logic between -cc1 and linker
> // invocations.
> static bool exceptionSettings(const ArgList &Args, const llvm::Triple
> &Triple) {
> @@ -1947,15 +1930,21 @@ static void addExceptionArgs(const ArgLi
> // Gather the exception settings from the command line arguments.
> bool EH = exceptionSettings(Args, Triple);
>
> - // Obj-C exceptions are enabled by default, regardless of -fexceptions.
> This
> - // is not necessarily sensible, but follows GCC.
> - if (types::isObjC(InputType) &&
> - Args.hasFlag(options::OPT_fobjc_exceptions,
> - options::OPT_fno_objc_exceptions,
> - true)) {
> - CmdArgs.push_back("-fobjc-exceptions");
> + if (types::isObjC(InputType)) {
> + bool ObjCExceptionsEnabled = true;
> + if (Arg *A = Args.getLastArg(options::OPT_fobjc_exceptions,
> + options::OPT_fno_objc_exceptions,
> + options::OPT_fexceptions,
> + options::OPT_fno_exceptions))
> + ObjCExceptionsEnabled =
> + A->getOption().matches(options::OPT_fobjc_exceptions) ||
> + A->getOption().matches(options::OPT_fexceptions);
> +
> + if (ObjCExceptionsEnabled) {
> + CmdArgs.push_back("-fobjc-exceptions");
>
> - EH |= shouldUseExceptionTablesForObjCExceptions(objcRuntime, Triple);
> + EH = true;
> + }
> }
>
> if (types::isCXX(InputType)) {
>
> Removed: cfe/trunk/test/Driver/exceptions.m
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/exceptions.m?rev=223454&view=auto
>
> ==============================================================================
> --- cfe/trunk/test/Driver/exceptions.m (original)
> +++ cfe/trunk/test/Driver/exceptions.m (removed)
> @@ -1,19 +0,0 @@
> -// RUN: %clang -target x86_64-apple-darwin9 \
> -// RUN: -fsyntax-only -fno-exceptions %s
> -
> -void f1() {
> - @throw @"A";
> -}
> -
> -void f0() {
> - @try {
> - f1();
> - } @catch (id x) {
> - ;
> - }
> -}
> -
> -int main() {
> - f0();
> - return 0;
> -}
>
> Added: cfe/trunk/test/Driver/exceptions.mm
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/exceptions.mm?rev=223455&view=auto
>
> ==============================================================================
> --- cfe/trunk/test/Driver/exceptions.mm (added)
> +++ cfe/trunk/test/Driver/exceptions.mm Fri Dec 5 02:56:55 2014
> @@ -0,0 +1,6 @@
> +// RUN: %clang -target x86_64-apple-darwin11 -fno-exceptions %s -o - -###
> 2>&1 | \
> +// RUN: FileCheck %s
> +
> +CHECK-NOT: "-fobjc-exceptions"
> +CHECK-NOT: "-fcxx-exceptions"
> +CHECK-NOT: "-fexceptions"
>
> Modified: cfe/trunk/test/Driver/rewrite-legacy-objc.m
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Driver/rewrite-legacy-objc.m?rev=223455&r1=223454&r2=223455&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/Driver/rewrite-legacy-objc.m (original)
> +++ cfe/trunk/test/Driver/rewrite-legacy-objc.m Fri Dec 5 02:56:55 2014
> @@ -9,5 +9,5 @@
> // RUN: FileCheck -check-prefix=TEST1 %s
> // RUN: %clang -no-canonical-prefixes -target i386-apple-macosx10.6.0
> -rewrite-legacy-objc %s -o - -### 2>&1 | \
> // RUN: FileCheck -check-prefix=TEST2 %s
> -// TEST1: "-fmessage-length" "0" "-stack-protector" "1" "-mstackrealign"
> "-fblocks" "-fobjc-runtime=macosx-fragile"
> "-fobjc-subscripting-legacy-runtime" "-fencode-extended-block-signature"
> "-fno-objc-infer-related-result-type" "-fobjc-exceptions"
> "-fmax-type-align=16" "-fdiagnostics-show-option"
> -// TEST2: "-fmessage-length" "0" "-stack-protector" "1" "-mstackrealign"
> "-fblocks" "-fobjc-runtime=macosx-fragile"
> "-fencode-extended-block-signature" "-fno-objc-infer-related-result-type"
> "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
> +// TEST1: "-fmessage-length" "0" "-stack-protector" "1" "-mstackrealign"
> "-fblocks" "-fobjc-runtime=macosx-fragile"
> "-fobjc-subscripting-legacy-runtime" "-fencode-extended-block-signature"
> "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions"
> "-fmax-type-align=16" "-fdiagnostics-show-option"
> +// TEST2: "-fmessage-length" "0" "-stack-protector" "1" "-mstackrealign"
> "-fblocks" "-fobjc-runtime=macosx-fragile"
> "-fencode-extended-block-signature" "-fno-objc-infer-related-result-type"
> "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16"
> "-fdiagnostics-show-option"
>
>
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