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Don't trap exceptions if a debugger is detected on Windows.
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Having to "step into" the program every time you debug it to set
rt_trapExceptions to false is a nuisance (perhaps more so with Windows
debuggers than GDB). Fortunately, we can easily detect when our D program
is run under a debugger, and disable the default exception handler, so
that an uncaught exception will be handled by the debugger.

I believe other Windows runtimes (C++/Delphi) do this as well.
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@CyberShadow
CyberShadow committed Feb 24, 2012
1 parent 54ee857 commit 1e48655
Showing 1 changed file with 7 additions and 0 deletions.
7 changes: 7 additions & 0 deletions src/rt/dmain2.d
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Expand Up @@ -36,6 +36,7 @@ version (Windows)
extern (Windows) wchar_t* GetCommandLineW();
extern (Windows) wchar_t** CommandLineToArgvW(wchar_t*, int*);
extern (Windows) export int WideCharToMultiByte(uint, uint, wchar_t*, int, char*, int, char*, int);
extern (Windows) int IsDebuggerPresent();
pragma(lib, "shell32.lib"); // needed for CommandLineToArgvW
}

Expand Down Expand Up @@ -418,6 +419,12 @@ extern (C) int main(int argc, char** argv)

bool trapExceptions = rt_trapExceptions;

version (Windows)
{
if (IsDebuggerPresent())
trapExceptions = false;
}

void tryExec(scope void delegate() dg)
{
void printLocLine(Throwable t)
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5 comments on commit 1e48655

@jkm
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@jkm jkm commented on 1e48655 Sep 13, 2012

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How do you "step into" the program?
I'm trying to debug my program but I cannot stop the runtime from handling the Throwable. My minimal example is:

extern extern(C) __gshared bool rt_trapExceptions;                              
static this()                                                                   
{                                                                               
    rt_trapExceptions = false;                                                  
}                                                                               

void main()                                                                     
{                                                                               
    throw new Exception("test");                                                
}

But this still prints the backtrace.
I'm using the rt_trapExceptions because I'm running Linux.

@alexrp
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@alexrp alexrp commented on 1e48655 Sep 13, 2012

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On Linux, just break on _d_throwc.

@jkm
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@jkm jkm commented on 1e48655 Sep 13, 2012

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Many thanks. I would have never found this myself. I'll give it a try.

@CyberShadow
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You can't set rt_trapExceptions from your program, because it is read before any of your code runs (incl. static constructors). It must be set from a debugger.

@jkm
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@jkm jkm commented on 1e48655 Sep 13, 2012

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Meaning the debugger sets the variable and then calls main?
But anyway I do not understand the commit message then.

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