how to debug exceptions/asserts thrown in module constructors?

[Timothee Cour via Digitalmars-d-learn]

UPDATE:

* b Loader.d:123 didn't help either:

error: parsing line table prologue at 0x00000000 (parsing ended around
0x00000000
Breakpoint 1: where = mybinary.temp`D4gtkc6Loader6Linker12_staticDtor3FZv,
address = 0x0000000100315410
(process exited despite breakpoint); dmd's dwarf debug info seems incorrect

* b _d_throwc #does nothing

* b _d_print_throwable: doesn't show useful context (only shows backtrace
after stack unwinding)
(lldb) bt
* thread #1: tid = 0x6187c1, 0x0000000100191c30 mybinary.temp
_d_print_throwable, stop reason = breakpoint 4.1
  * frame #0: 0x0000000100191c30 mybinary.temp _d_print_throwable
    frame #1: 0x0000000100191530 mybinary.temp rt_init + 160
    frame #2: 0x0000000100191a9a mybinary.temp
D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ6runAllMFZv
+ 14
    frame #3: 0x0000000100191a40 mybinary.temp D2rt6dmain211_d_run_
mainUiPPaPUAAaZiZ7tryExecMFMDFZvZv + 36
    frame #4: 0x00000001001919a6 mybinary.temp _d_run_main + 498
    frame #5: 0x0000000100001efa mybinary.temp main + 34
    frame #6: 0x00007fff89ad65ad libdyld.dylib start + 1

* b _D4gtkc6Loader6Linker11loadLibraryFAyaZv isn't very helpful since this
function is complex (and could be inlined more generally) and that function
is called many times before the exception is thrown
```
  public static void loadLibrary(string library)
  {
    void* handle = pLoadLibrary(library);

    //TODO: A more general way to try more than one version.
    if ( handle is null && library == importLibs[LIBRARY.GSV] )
      handle = pLoadLibrary(importLibs[LIBRARY.GSV1]);

    if ( handle is null )
      throw new Exception("Library load failed: " ~ library);

    loadedLibraries[library] = handle;
  }
```

but at least we get a better context:

(lldb) bt
* thread #1: tid = 0x6187c1, 0x0000000100315878 mybinary.temp
D4gtkc6Loader6Linker11loadLibraryFAyaZv, stop reason = breakpoint 3.1
  * frame #0: 0x0000000100315878 mybinary.temp
D4gtkc6Loader6Linker11loadLibraryFAyaZv
    frame #1: 0x0000000100315699 mybinary.temp
D4gtkc6Loader6Linker9getSymbolFAyaAAyaXPv + 237
    frame #2: 0x00000001003155a4 mybinary.temp
D4gtkc6Loader6Linker9getSymbolFAyaAE4gtkc5paths7LIBRARYXPv + 232
    frame #3: 0x00000001003163bd mybinary.temp D4gtkc6Loader6Linker39__
T4linkTPUZE4gtkc12gobjecttypes5GTypeZ4linkFKPUZE4gtkc12gobje
cttypes5GTypeAyaAE4gtkc5paths7LIBRARYXv + 69 at
.dub/packages/gtk-d-3.3.1/gtk-d/src/gtkc/Loader.d:46
    frame #4: 0x000000010038c75d mybinary.temp
D4gtkc3atk18_sharedStaticCtor4FZv
+ 77 at .dub/packages/gtk-d-3.3.1/gtk-d/src/gtkc/atk.d:36
    frame #5: 0x000000010038c67d mybinary.temp _D4gtkc3atk15__modsharedctorFZv
+ 9 at .dub/packages/gtk-d-3.3.1/gtk-d/src/gtkc/atk.d:32
    frame #6: 0x0000000100199c17 mybinary.temp D2rt5minfo67__
T14runModuleFuncsS442rt5minfo11ModuleGroup8runCtorsMFZ9__
lambda2Z14runModuleFuncsMFAxPyS6object10ModuleInfoZv + 91
    frame #7: 0x0000000100199785 mybinary.temp
D2rt5minfo11ModuleGroup8runCtorsMFZv + 37
    frame #8: 0x0000000100199a91 mybinary.temp
D2rt5minfo13rt_moduleCtorUZ14__foreachbody1MFKS2rt19sections_osx_x86_6412SectionGroupZi
+ 45
    frame #9: 0x0000000100199a60 mybinary.temp rt_moduleCtor + 20
    frame #10: 0x00000001001914f3 mybinary.temp rt_init + 99
    frame #11: 0x0000000100191a9a mybinary.temp
D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ6runAllMFZv
+ 14
    frame #12: 0x0000000100191a40 mybinary.temp D2rt6dmain211_d_run_
mainUiPPaPUAAaZiZ7tryExecMFMDFZvZv + 36
    frame #13: 0x00000001001919a6 mybinary.temp _d_run_main + 498
    frame #14: 0x0000000100001efa mybinary.temp main + 34
    frame #15: 0x00007fff89ad65ad libdyld.dylib start + 1


Ideally there should be a way (via a runtime or compile time option) to
wrap the exception throwing (during rt_moduleCtor) inside a extern(C)
function that we can put a breakpoint on (and possibly even call
backtrace_symbols on)

On Sun, Nov 27, 2016 at 2:19 PM, Timothee Cour <thelastmammoth at gmail.com>
wrote:

> in the process of trying to debug https://github.com/
> BlackEdder/ggplotd/issues/32 I would like to get a stracktrace and/or put
> a breakpoint before exception is thrown:
>
>
> ```
> lldb $binary
> r
> (lldb)
> Process 34168 resuming
> object.Exception at ../../../../.dub/packages/gtk-d-3.3.1/gtk-d/src/gtkc/Loader.d(123):
> Library load failed: libatk-1.0.dylib
> Process 34168 exited with status = 1 (0x00000001)
> ```
>
> Adding
> ```
> b _d_throwc #does nothing
> ```
>
> didn't help, also, it hasn't entered d main yet so `Runtime.traceHandler =
> &defaultTraceHandler;` isn't helpful.
>
> The fix here was to lookup the code, find the corresponding mangled name
> location and add a breakpoint via `b _D4gtkc6Loader6Linker11loadLibraryFAyaZv`
> but is there a general fix?
>
>
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