[cfe-dev] [llvm] r193937 - When LLVM is embedded in a larger application, it's not OK for LLVM to intercept crashes. LLVM already has

[Filip Pizlo]

On Nov 2, 2013, at 9:15 PM, Alp Toker <alp at nuanti.com> wrote:

> Brilliant. Could you revert the API addition of
> LLVMDisablePrettyStackTrace() in r193937 while we figure this out?

I'd rather not.  Without this function, it's impossible for a C API client to embed LLVM.

I agree that there is a better solution out there, but I'd rather have this as a stop-gap until then.  Is there any real harm to having this in the tree in the meantime?  Because there is clear harm on my end from removing it - namely, the usual crash recording machinery for OS X applications doesn't work as soon as LLVM is embedded.

-Filip


> 
> The new approach will be a step towards cleaning up libclang as well:
> 
> tools/libclang/CIndex.cpp-  // Disable pretty stack trace functionality,
> which will otherwise be a very
> tools/libclang/CIndex.cpp-  // poor citizen of the world and set up all
> sorts of signal handlers.
> tools/libclang/CIndex.cpp:  llvm::DisablePrettyStackTrace = true;
> 
> Thanks for noticing the issue and starting on a solution!
> 
> Alp.
> 
> 
> On 03/11/2013 04:10, Filip Pizlo wrote:
>> 
>> On Nov 2, 2013, at 9:07 PM, Alp Toker <alp at nuanti.com
>> <mailto:alp at nuanti.com>> wrote:
>> 
>>> Could we make this the default, then provide
>>> LLVMEnablePrettyStackTrace() instead?
>> 
>> I like this.
>> 
>>> 
>>> By definition the C API is for embedding, and embedders don't expect
>>> each API they use to install global signal handlers.
>> 
>> Right, and we could also do the same thing for the fatal error
>> handler.  The default fatal error handler does exit(1), which is
>> clearly not right for embedders.
>> 
>> It seems like both the pretty stack traces and the fatal error handler
>> could be manually enabled by those clients that depend on it.
>> 
>>> 
>>> Alp.
>>> 
>>> 
>>> On 03/11/2013 00:29, Filip Pizlo wrote:
>>>> Author: fpizlo
>>>> Date: Sat Nov  2 19:29:47 2013
>>>> New Revision: 193937
>>>> 
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=193937&view=rev
>>>> Log:
>>>> When LLVM is embedded in a larger application, it's not OK for LLVM
>>>> to intercept crashes.  LLVM already has 
>>>> the ability to disable this functionality.  This patch exposes it
>>>> via the C API.
>>>> 
>>>> 
>>>> Modified:
>>>>   llvm/trunk/include/llvm-c/Core.h
>>>>   llvm/trunk/lib/Support/PrettyStackTrace.cpp
>>>> 
>>>> Modified: llvm/trunk/include/llvm-c/Core.h
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm-c/Core.h?rev=193937&r1=193936&r2=193937&view=diff
>>>> ==============================================================================
>>>> --- llvm/trunk/include/llvm-c/Core.h (original)
>>>> +++ llvm/trunk/include/llvm-c/Core.h Sat Nov  2 19:29:47 2013
>>>> @@ -434,6 +434,12 @@ void LLVMInstallFatalErrorHandler(LLVMFa
>>>> void LLVMResetFatalErrorHandler(void);
>>>> 
>>>> /**
>>>> + * Disable LLVM's built-in stack trace code. This must be called
>>>> before any
>>>> + * other LLVM APIs; otherwise the results are undefined.
>>>> + */
>>>> +void LLVMDisablePrettyStackTrace(void);
>>>> +
>>>> +/**
>>>> * @defgroup LLVMCCoreContext Contexts
>>>> *
>>>> * Contexts are execution states for the core LLVM IR system.
>>>> 
>>>> Modified: llvm/trunk/lib/Support/PrettyStackTrace.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/PrettyStackTrace.cpp?rev=193937&r1=193936&r2=193937&view=diff
>>>> ==============================================================================
>>>> --- llvm/trunk/lib/Support/PrettyStackTrace.cpp (original)
>>>> +++ llvm/trunk/lib/Support/PrettyStackTrace.cpp Sat Nov  2 19:29:47 2013
>>>> @@ -20,6 +20,7 @@
>>>> #include "llvm/Support/ThreadLocal.h"
>>>> #include "llvm/Support/Watchdog.h"
>>>> #include "llvm/Support/raw_ostream.h"
>>>> +#include "llvm-c/Core.h"
>>>> 
>>>> #ifdef HAVE_CRASHREPORTERCLIENT_H
>>>> #include <CrashReporterClient.h>
>>>> @@ -147,3 +148,7 @@ void PrettyStackTraceProgram::print(raw_
>>>>    OS << ArgV[i] << ' ';
>>>>  OS << '\n';
>>>> }
>>>> +
>>>> +void LLVMDisablePrettyStackTrace() {
>>>> +  DisablePrettyStackTrace = true;
>>>> +}
>>>> 
>>>> 
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>>> 
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>> 
> 
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