similar to: Resurrect Bug18710 (Only generate .ARM.exidx and ARM.extab when needed with EHABI)

Is it possible to force llvm/clang to not create a .ARM.exidx section for a bare-metal application that does not use exceptions? I've tried -fno-exceptions -fno-unwind-tables, but it still generates the section with all functions marked as 'cantunwind'. As a temporary punt I tried linking (using lld) with /DISCARD/ on the section, but that seemed to crash lld, which is another

Appreciate the response - explanation makes sense. It might be desirable to have something like '-fno-exceptions -fno-unwind-tables' really kill that section but I won't push that argument. As to the lld issue, I was seeing a crash in 6.0.1. This was specifically just using: "/DISCARD/ : { *(.ARM.exidx*) }". I tried this morning with 7.0.0 and it did not reproduce, so call

Hello > My question is, to avoid duplicate effort, > does someone take charge of this part? or > does anyone is already implementing this currently? > > BTW, any suggestion on this effort? I'm very appreciated! There are several directions here: 1. Binary emission. Right now MC layer is text-only and depends on assembler 2. Correctness issues. It's believed that unwinding

Dear Renato and Anton, Big thanks to your help. Those references are very helpful! BTW, After I applying this patch from Logan Chien, I pass some examples on ARM assembly emission. It seems good to me. http://llvm.org/bugs/show_bug.cgi?id=7187#attach_9161 For object file emission, The first thing is making MC generate correct .ARM.exidx and .ARM.extab. I will keep tracing that. Thanks!

Dear all, AFAIK, ARM EHABI is not ready for both asm and obj emitter. Some people including me what to implement them. My question is, to avoid duplicate effort, does someone take charge of this part? or does anyone is already implementing this currently? BTW, any suggestion on this effort? I'm very appreciated! Thanks in advance! -- Best regards, Wen-Han Gu (Nowar) -------------- next

I'd love to hear more details. Are you saying that this infinite loop is a limitation of EHABI table format, and not something that can be fixed in the compiler? Meanwhile, please notice that gcc behavior matches current clang behavior that I described above. We would not want to create an incompatibility. On Fri, Feb 14, 2014 at 8:42 PM, Logan Chien <tzuhsiang.chien at gmail.com>

I assume this "CantUnwind table" is not the same as Unwind table index '.ARM.exidx' at offset 0x818 contains 4 entries: 0x5d4 <main>: 0x1 [cantunwind] because the latter prevent any unwinding, breaking debuggers/profilers/sanitizers. As I understand, the right way to enable basic unwind through any function (without emitting landing pands etc, unless they are needed for

from http://llvm.org/docs/LangRef.html: nounwind > This function attribute indicates that the function never raises an > exception. If the function does raise an exception, its runtime behavior is > undefined. However, functions marked nounwind may still trap or generate > asynchronous exceptions. Exception handling schemes that are recognized by > LLVM to handle asynchronous

>> The semantics uwtable is just "make sure it is possible to unwind past >> this function". It doesn't include anything more, >> like the ability to run destructors. It is used for ABIs that require >> it for use in debuggers and profilers. > > Well, that meaning fails when you have both uwtable and nounwind, > which means: "generate a

On Thu, Feb 13, 2014 at 5:39 PM, Renato Golin <renato.golin at linaro.org> wrote: > On 13 February 2014 11:35, Evgeniy Stepanov <eugenis at google.com> wrote: >> Unwind table index '.ARM.exidx' at offset 0x818 contains 4 entries: >> 0x5d4 <main>: 0x1 [cantunwind] > > This is exactly what I meant. > > >> because the latter prevent any

> On Feb 8, 2017, at 12:58 PM, Reid Kleckner via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > I think this behavior is intended to allow better LTO between C and C++. Consider this kind of code: > > // foo.h > extern "C" int doThing(bool canThrow); > // foo.cpp > int doThing(bool canThrow) { > ... > if (hadError) { > if (canThrow)

On 21 March 2014 18:47, Logan Chien <tzuhsiang.chien at gmail.com> wrote: > * There's the table for ARM target: > > - no attribute => emit unwind table > - with nounwind => emit unwind table with cantunwind > - with uwtable => emit unwind table > - with uwtable+nounwind => emit unwind table WITHOUT the cantunwind > > The cantunwind record will stop the

Hi Peter, Thanks for your response. > On 18 Nov 2019, at 17:44, Peter Smith <peter.smith at linaro.org> wrote: > > On Mon, 18 Nov 2019 at 12:32, Sergej Jaskiewicz via llvm-dev > <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote: >> >> There’s this bug: https://bugs.llvm.org/show_bug.cgi?id=38468

I'm cross compiling using clang for x86_64 windows using SEH exceptions. If at all possible, I would like to enable unwind tables to be generated in debug_frame, but I was unable to figure out how to accomplish this. Is there a supported way? Thanks, Keno

> On 18 Nov 2019, at 19:55, Peter Smith <peter.smith at linaro.org> wrote: > > On Mon, 18 Nov 2019 at 15:23, Sergej Jaskiewicz <jaskiewiczs at icloud.com <mailto:jaskiewiczs at icloud.com>> wrote: >> >> Hi Peter, >> >> Thanks for your response. >> >> On 18 Nov 2019, at 17:44, Peter Smith <peter.smith at linaro.org> wrote:

> On 18 Nov 2019, at 22:11, Peter Smith <peter.smith at linaro.org> wrote: > > On Mon, 18 Nov 2019 at 17:06, Sergej Jaskiewicz <jaskiewiczs at icloud.com <mailto:jaskiewiczs at icloud.com>> wrote: >> >> >> >> On 18 Nov 2019, at 19:55, Peter Smith <peter.smith at linaro.org> wrote: >> >> On Mon, 18 Nov 2019 at 15:23, Sergej

There’s this bug: https://bugs.llvm.org/show_bug.cgi?id=38468. I’ve managed to track it down to a configuration issue. The thing is that in order for libunwind to be usable on ARM Linux, it should be built with the -funwind-tables flag. This flag is conditionally set here: https://github.com/llvm/llvm-project/blob/master/libunwind/CMakeLists.txt#L294, if the compiler “supports” it. However, the

Hi all,         I found some problem when trying to use exception handling with LLVM (SVN revision 152113) + clang combination (SVN revision 152115). I am observing failure in __gnu_unwind_pr_common unwind-arm.c (gcc/config/arm dir in gcc 4.5.3 source). Personality routine 0 is used.           Inside __gnu_unwind_pr_common after "switch (((offset & 1) << 1) | (len & 1))"

On 15 March 2014 17:06, Logan Chien <tzuhsiang.chien at gmail.com> wrote: > I would like to know what do you mean by "commoning them up"? Hi Logan, That'd be reducing ARM directives in favour of CFI, but as I said (and you too), GNU compatibility will probably be an issue for a very long time. > For the space issue, I personally don't think this is a big issue.

On 20 March 2014 02:09, Rafael Espíndola <rafael.espindola at gmail.com> wrote: > I think this is just 2. It uses .eh_frame for unwinding proper. The > only difference in .eh_frame is that there is a personality function > defined. If there is no debug information, it should still be possible to unwind the stack via the saved LR on the stack, no? If there is only line info, you