Using a variable exported by a dll in a local variable: crash

[alban_c]

Hi,

I am writing an "hello world" program with a dll. I compile and test it with CodeWarrior and Carbide.

When I use the symbol exported by the .dll with a specific pattern, my program crashs. It does not reach the beakpoint I setup on the main() function: it crashs before the main() function. The pattern is this line:

  mystruct_t *f[1] = {myvar}; 

where myvar is a variable exported by the dll and f is a local variable.

If change this line with the 2 following lines, it works:

  mystruct_t *f[1];
  f[0] = myvar; 

See the full sources below.

Is it the expected behaviour, or a known bug?

testdll.c:

typedef char * (*ptrfunc_t)(char *);
struct mystruct_s
{
        ptrfunc_t a;
        ptrfunc_t b;
};
typedef struct mystruct_s mystruct_t;

__declspec(dllexport) char *func(char *a)
{
        printf("func: '%s'\n", a);
        sleep(5);
        return "";
}

__declspec(dllexport) mystruct_t myvar[1] = {{func, func}}; 

testexe.c:

typedef char * (*ptrfunc_t)(char *);
struct mystruct_s
{
        ptrfunc_t a;
        ptrfunc_t b;
};
typedef struct mystruct_s mystruct_t;

__declspec(dllimport) mystruct_t myvar[];


int main(int argc, char *argv[])
{
        char *t;

        mystruct_t *f[1] = {myvar};
        /*
        mystruct_t *f[1];
        f[0] = myvar;
        */

        printf("Hello world\n");
        sleep(5);
        return 0;
} 

Thanks

[alban_c]

I forget to say I am using S60_3rd_Ed_SDK_FP2_Beta_b.

And I use EPOCALLOWDLLDATA in .mmp files (both for the exe and the dll).

[wizard_hu_]

http://wiki.forum.nokia.com/index.ph...ded_panic_code

[alban_c]

http://wiki.forum.nokia.com/index.ph...ded_panic_code

Thank you for the link.

The panic code I get is:

Application closed:
Main
KERN-EXEC 3 

The documentation says: "KERN-EXEC 3 means a general unhandled exception."

Then I enabled the just-in-time debugging and when the application crashes, the debugger prints the stack:

Thread [Thread id: 17780] (Suspended: Signal 'Halt' received. Description: User halted thread.)
20 0x8395F6( ekern.exe )() 0x008395f6
19 0x8397DB( ekern.exe )() 0x008397db
18 0x84C0C4( ekern.exe )() 0x0084c0c4
17 0x8625FE( ekern.exe )() 0x008625fe
16 0x862422( ekern.exe )() 0x00862422
15 0x832138( ekern.exe )() 0x00832138
14 0x8318FC( ekern.exe )() 0x008318fc
13 0x831186( ekern.exe )() 0x00831186
12 0x8326C4( ekern.exe )() 0x008326c4
11 0x862842( ekern.exe )() 0x00862842
10 0x8587B4( ekern.exe )() 0x008587b4
9 0x858780( ekern.exe )() 0x00858780
8 0x838DE1( ekern.exe )() 0x00838de1
7 0x837107( ekern.exe )() 0x00837107
6 0x837175( ekern.exe )() 0x00837175
5 0x47A1005( testexe.exe )() 0x047a1005
4 _E32Startup() F:\src\cedar\generic\base\e32\EUSER\epoc\win32\uc_exe.cpp:72 0x047a1123
3 0x83880F( ekern.exe )() 0x0083880f
2 0x836DC4( ekern.exe )() 0x00836dc4
1 0x7C80B683( KERNEL32.dll )() 0x7c80b683

[wizard_hu_]

You should click on "5" (I guess that testexe.exe is the code you are experimenting with). KERN-EXEC 3 is often related to accessing NULL/invalid pointers.

[alban_c]

You should click on "5" (I guess that testexe.exe is the code you are experimenting with). KERN-EXEC 3 is often related to accessing NULL/invalid pointers.

Yes testexe.exe is the code I am experimenting with. The code is available in my first comment (see testexe.c).

When I click on "5", Carbide does not open any code. Other lines don't open any code either, except "4" that print an error message because the source file is not available on my computer (uc_exe.cpp is not part of my project).

But I know it is because of the "mystruct_t *f[1] = {myvar};" line because if I remove it, it works.

I explained in my first comment how to change that line to get it work, but I would like to know the explanation.