Shared library / Mach-O: Application crashs if I call a function

[Hans Stoessel]

Hi, me again

Meanwhile, I can load the shared library in my Mach-O Application and I
found my function (BeepTwice) in
it. But if I try to call this function, the system crashs with the message:
"unknown PowerPC" exception, in the debugger there is an invalid opcode.

I have a test application (Mach-O bundle) and a
shared library which I want load in the test application.

Here is the code I use:

//--------------------------------------------------------------------------
// Test application: Test.cpp
//--------------------------------------------------------------------------
static pascal int (*beepTwice) (void);

static pascal OSErr loadLibrary()
{
OSErr myerr;
CFragConnectionID connID = kInvalidID;
FSSpec fsSpec;
CFragSymbolClass symClass;

myerr = FSMakeFSSpec(0, 0, "\pShlb4DOpen", &fsSpec);
myerr = GetDiskFragment(&fsSpec,
0,
kCFragGoesToEOF,
NULL,
kLoadCFrag,
&connID,
NULL,
NULL);

myerr = FindSymbol (connID, "\pBeepTwice",
(Ptr*) &beepTwice, &symClass);
//--------------------
// No error until here
//--------------------

beepTwice(); // Here the application crashs

return myerr;
}


//--------------------------------------------------------------------------
// Shared Library: BeepTwice.c
//--------------------------------------------------------------------------
#include <Sound.h>

#pragma export on

int BeepTwice ( void );

#pragma export off

int BeepTwice (void)
{
SysBeep(2);
SysBeep(2);
return 0;
}

Is it maybe a C/C++ problem?
Or a problem with the keyword pascal?
Is it a problem between Mach-O and the shared library?
Is there another way to call the function?

Thanks and Regards
Hans

[Hans Stoessel]

Hi, me again

Meanwhile, I can load the shared library in my Mach-O Application and I
found my function (BeepTwice) in
it. But if I try to call this function, the system crashs with the message:
"unknown PowerPC" exception, in the debugger there is an invalid opcode.

I have a test application (Mach-O bundle) and a
shared library which I want load in the test application.

Here is the code I use:

//--------------------------------------------------------------------------
// Test application: Test.cpp
//--------------------------------------------------------------------------
static pascal int (*beepTwice) (void);

static pascal OSErr loadLibrary()
{
OSErr myerr;
CFragConnectionID connID = kInvalidID;
FSSpec fsSpec;
CFragSymbolClass symClass;

myerr = FSMakeFSSpec(0, 0, "\pShlb4DOpen", &fsSpec);
myerr = GetDiskFragment(&fsSpec,
0,
kCFragGoesToEOF,
NULL,
kLoadCFrag,
&connID,
NULL,
NULL);

myerr = FindSymbol (connID, "\pBeepTwice",
(Ptr*) &beepTwice, &symClass);
//--------------------
// No error until here
//--------------------

beepTwice(); // Here the application crashs

return myerr;
}


//--------------------------------------------------------------------------
// Shared Library: BeepTwice.c
//--------------------------------------------------------------------------
#include <Sound.h>

#pragma export on

int BeepTwice ( void );

#pragma export off

int BeepTwice (void)
{
SysBeep(2);
SysBeep(2);
return 0;
}

Is it maybe a C/C++ problem?
Or a problem with the keyword pascal?
Is it a problem between Mach-O and the shared library?
Is there another way to call the function?

Thanks and Regards
Hans

[Eric VERGNAUD]

> Here is the code I use:

>
> //--------------------------------------------------------------------------
> // Test application: Test.cpp
> //--------------------------------------------------------------------------
> static pascal int (*beepTwice) (void);
>
> static pascal OSErr loadLibrary()
> {
> OSErr myerr;
> CFragConnectionID connID = kInvalidID;
> FSSpec fsSpec;
> CFragSymbolClass symClass;
>
> myerr = FSMakeFSSpec(0, 0, "\pShlb4DOpen", &fsSpec);
> myerr = GetDiskFragment(&fsSpec,
> 0,
> kCFragGoesToEOF,
> NULL,
> kLoadCFrag,
> &connID,
> NULL,
> NULL);
>
> myerr = FindSymbol (connID, "\pBeepTwice",
> (Ptr*) &beepTwice, &symClass);
> //--------------------
> // No error until here
> //--------------------
>
> beepTwice(); // Here the application crashs
>
> return myerr;
> }
>

You're almost there:

You should write:

typedef pascal int (*beepTwiceProcPtr) (void);

static beepTwiceProcPtr beepTwice;

static pascal OSErr loadLibrary()
{
OSErr myerr;
CFragConnectionID connID = kInvalidID;
FSSpec fsSpec;
CFragSymbolClass symClass;

myerr = FSMakeFSSpec(0, 0, "\pShlb4DOpen", &fsSpec);
myerr = GetDiskFragment(&fsSpec,
0,
kCFragGoesToEOF,
NULL,
kLoadCFrag,
&connID,
NULL,
NULL);

myerr = FindSymbol (connID,"\pBeepTwice",(Ptr*) &beepTwice, &symClass);
(*beepTwice)();

return myerr;
}

Since 4D Open uses 2 byte alignment, you should also make sure that any
struct declaration is enclosed by align pragmas.

Good luck.

Eric