llvm dev - Jun 2018 - runStaticConstructorsDestructors() causes crash on exit

On Alex's advice I am switching from MCJIT to the Orc API to compile and
execute functions. Starting from the new clang-interpreter example in the
source code (top of the tree!), I am able to execute my functions all
right... as long as there are no constructors and destructors to call.

My question: is there a simple way, with the Orc API, to run a module's
constructors and destructors? I see how OrcMCJITReplacement does it,
calling getConstructors() and getDestructors() when a module is added, and
running them later using a layer, but is there maybe a simpler way that I
am missing? I would prefer to avoid having to invent secret names for
constructors, play with their linkage and visibility, and generally get
involved in things I don't understand...

Thanks,
Geoff

On Fri, 15 Jun 2018 at 11:23, Alex Denisov <1101.debian at gmail.com>
wrote:
> Hi Geoff,
>
> I hit the same problem some time ago.
> The problem that atexit handlers are registered from the JITted code, and
> the handlers point to the memory allocated by JIT.
> When the host program exits it calls the atexit handlers, but the memory
> is already deallocated by JIT.
> That's basically the reason of the crash.
>
> From what I see ExecutionEngine and MCJIT do not provide any helpful API
> for this case.
> I can only recommend switching to Orc APIs in this case: there you can use
> custom symbol resolver and redirect atexit functions to your own
> function(s).
> That function would record atexit handlers, which you can call manually
> after running your program.
> Orc APIs even provide a class for that: orc::LocalCXXRuntimeOverrides.
>
> I think this is the right place to ask such questions.
> Otherwise, feel free to ping me on #llvm (AlexDenisov) if you need some
> hints on how to JIT native code using Orc APIs.
>
> I hope it helps.
>
> Cheers,
> Alex.
>
> > On 14. Jun 2018, at 12:44, Geoff Levner via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >
> > Greetings, LLVM wizards.
> >
> > I am using clang to compile a C++ module, and an ExecutionEngine
(MCJIT)
> to execute a function it defines. That works (or pretends to). However, if
> I call the module's constructors first:
> >
> > exec_engine->runStaticConstructorsDestructors(false);
> > exec_engine->runFunctionAsMain(function, argvec, NULL);
> >
> > execution still works, but my program crashes when it exits, in
> __run_exit_handlers(). I can't tell from gdb what exit handler is
crashing,
> but no calls are made to atexit() or on_exit(); all exit handlers are
> installed via __cxa_atexit().
> >
> > This may or may not be meaningful, but I am forced to compile with
> -fno-use-cxa-atexit, otherwise clang complains that __dso_handle could not
> be resolved.
> >
> > Any guidance would be MUCH appreciated. I am at a loss... Also, if you
> know of a better place to look for help than this mailing list, that would
> be appreciated, too.
> >
> > Thanks,
> > Geoff
>
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Hi Geoff,

As far as I know there is no "simple" way to do that.
> I would prefer to avoid having to invent secret names for constructors,
play with their linkage and visibility, and generally get involved in things I
don't understand...
What do you mean by "invent secret names"? If you don't need to
JIT native object files, but only bitcode, then MCJIT' approach should work.
Just use that "snippet" in your code :)
> On 19. Jun 2018, at 17:54, Geoff Levner <glevner at gmail.com> wrote:
> 
> On Alex's advice I am switching from MCJIT to the Orc API to compile
and execute functions. Starting from the new clang-interpreter example in the
source code (top of the tree!), I am able to execute my functions all right...
as long as there are no constructors and destructors to call.
> 
> My question: is there a simple way, with the Orc API, to run a module's
constructors and destructors? I see how OrcMCJITReplacement does it, calling
getConstructors() and getDestructors() when a module is added, and running them
later using a layer, but is there maybe a simpler way that I am missing? I would
prefer to avoid having to invent secret names for constructors, play with their
linkage and visibility, and generally get involved in things I don't
understand...
> 
> Thanks,
> Geoff
> 
> On Fri, 15 Jun 2018 at 11:23, Alex Denisov <1101.debian at gmail.com>
wrote:
> Hi Geoff,
> 
> I hit the same problem some time ago.
> The problem that atexit handlers are registered from the JITted code, and
the handlers point to the memory allocated by JIT.
> When the host program exits it calls the atexit handlers, but the memory is
already deallocated by JIT.
> That's basically the reason of the crash.
> 
> From what I see ExecutionEngine and MCJIT do not provide any helpful API
for this case.
> I can only recommend switching to Orc APIs in this case: there you can use
custom symbol resolver and redirect atexit functions to your own function(s).
> That function would record atexit handlers, which you can call manually
after running your program.
> Orc APIs even provide a class for that: orc::LocalCXXRuntimeOverrides.
> 
> I think this is the right place to ask such questions.
> Otherwise, feel free to ping me on #llvm (AlexDenisov) if you need some
hints on how to JIT native code using Orc APIs.
> 
> I hope it helps.
> 
> Cheers,
> Alex.
> 
> > On 14. Jun 2018, at 12:44, Geoff Levner via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> >
> > Greetings, LLVM wizards.
> >
> > I am using clang to compile a C++ module, and an ExecutionEngine
(MCJIT) to execute a function it defines. That works (or pretends to). However,
if I call the module's constructors first:
> >
> > exec_engine->runStaticConstructorsDestructors(false);
> > exec_engine->runFunctionAsMain(function, argvec, NULL);
> >
> > execution still works, but my program crashes when it exits, in
__run_exit_handlers(). I can't tell from gdb what exit handler is crashing,
but no calls are made to atexit() or on_exit(); all exit handlers are installed
via __cxa_atexit().
> >
> > This may or may not be meaningful, but I am forced to compile with
-fno-use-cxa-atexit, otherwise clang complains that __dso_handle could not be
resolved.
> >
> > Any guidance would be MUCH appreciated. I am at a loss... Also, if you
know of a better place to look for help than this mailing list, that would be
appreciated, too.
> >
> > Thanks,
> > Geoff
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When OrcMCJITReplacement is given a new module, it asks for the module's
constructors, gives them names like $static_ctor.0, $static_ctor.1, etc.,
and saves the mangled names in a map. Later, to execute them, it uses
runViaLayer(), which looks for those symbol names in the given JIT layer.
Could one not simply execute the constructors straight away, rather than
naming them and looking them up by name later, if there is only one module?

On Wed, 20 Jun 2018 at 23:08, Alex Denisov <1101.debian at gmail.com>
wrote:
> Hi Geoff,
>
> As far as I know there is no "simple" way to do that.
>
> > I would prefer to avoid having to invent secret names for
constructors,
> play with their linkage and visibility, and generally get involved in
> things I don't understand...
>
> What do you mean by "invent secret names"? If you don't need
to JIT native
> object files, but only bitcode, then MCJIT' approach should work. Just
use
> that "snippet" in your code :)
>
> > On 19. Jun 2018, at 17:54, Geoff Levner <glevner at gmail.com>
wrote:
> >
> > On Alex's advice I am switching from MCJIT to the Orc API to
compile and
> execute functions. Starting from the new clang-interpreter example in the
> source code (top of the tree!), I am able to execute my functions all
> right... as long as there are no constructors and destructors to call.
> >
> > My question: is there a simple way, with the Orc API, to run a
module's
> constructors and destructors? I see how OrcMCJITReplacement does it,
> calling getConstructors() and getDestructors() when a module is added, and
> running them later using a layer, but is there maybe a simpler way that I
> am missing? I would prefer to avoid having to invent secret names for
> constructors, play with their linkage and visibility, and generally get
> involved in things I don't understand...
> >
> > Thanks,
> > Geoff
> >
> > On Fri, 15 Jun 2018 at 11:23, Alex Denisov <1101.debian at
gmail.com>
> wrote:
> > Hi Geoff,
> >
> > I hit the same problem some time ago.
> > The problem that atexit handlers are registered from the JITted code,
> and the handlers point to the memory allocated by JIT.
> > When the host program exits it calls the atexit handlers, but the
memory
> is already deallocated by JIT.
> > That's basically the reason of the crash.
> >
> > From what I see ExecutionEngine and MCJIT do not provide any helpful
API
> for this case.
> > I can only recommend switching to Orc APIs in this case: there you can
> use custom symbol resolver and redirect atexit functions to your own
> function(s).
> > That function would record atexit handlers, which you can call
manually
> after running your program.
> > Orc APIs even provide a class for that: orc::LocalCXXRuntimeOverrides.
> >
> > I think this is the right place to ask such questions.
> > Otherwise, feel free to ping me on #llvm (AlexDenisov) if you need
some
> hints on how to JIT native code using Orc APIs.
> >
> > I hope it helps.
> >
> > Cheers,
> > Alex.
> >
> > > On 14. Jun 2018, at 12:44, Geoff Levner via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> > >
> > > Greetings, LLVM wizards.
> > >
> > > I am using clang to compile a C++ module, and an ExecutionEngine
> (MCJIT) to execute a function it defines. That works (or pretends to).
> However, if I call the module's constructors first:
> > >
> > > exec_engine->runStaticConstructorsDestructors(false);
> > > exec_engine->runFunctionAsMain(function, argvec, NULL);
> > >
> > > execution still works, but my program crashes when it exits, in
> __run_exit_handlers(). I can't tell from gdb what exit handler is
crashing,
> but no calls are made to atexit() or on_exit(); all exit handlers are
> installed via __cxa_atexit().
> > >
> > > This may or may not be meaningful, but I am forced to compile
with
> -fno-use-cxa-atexit, otherwise clang complains that __dso_handle could not
> be resolved.
> > >
> > > Any guidance would be MUCH appreciated. I am at a loss... Also,
if you
> know of a better place to look for help than this mailing list, that would
> be appreciated, too.
> > >
> > > Thanks,
> > > Geoff
>
>
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