QuickC 2.0 Routines Using malloc() Fail in QB Quick Library (57923)

MORE INFORMATION

C routines that use malloc() to allocate memory work correctly when linked with compiled Basic programs. Furthermore, these routines work correctly in Quick libraries when compiled with C Compiler version 5.0 and 5.1.

The following code example causes the above error (R6013) in the QuickBasic environment. The code is the SETMEM example from the QuickBasic QB Advisor online Help system, with one line added to reference the pointer.

Code Example

The example below uses the SETMEM function to free memory for a C function that uses the C routine malloc() to get dynamic memory.

Note: To run this program, you must separately compile the C function and put it in a Quick library. The C function must be compiled using the large memory model, so calls to malloc() use the far space freed by the Basic program.

  DECLARE SUB CFunc CDECL (BYVAL X AS INTEGER)
'Decrease the size of the far heap so CFunc can use malloc
'to get dynamic memory:
   BeforeCall = SETMEM(-2048)
'Call the C function:
   CFunc (1024)
'Return the memory to the far heap; use a larger value so
'all space goes back into the heap.
   AfterCall = SETMEM(3500)
   IF AfterCall <= BeforeCall THEN PRINT "Memory not reallocated."
   END


/* Filename: Setmemc.c,  C Function */ 
void far cfunc(bytes)
int bytes;
{
   char *malloc();
   char *workspace;

   /* Allocate working memory using amount Basic freed. */ 
   workspace=malloc((unsigned) bytes);

   /* Working space would be used here. */ 
   *workspace='X';    // Added line to reference ptr/cause error

   /* Free memory before returning to Basic. */ 
   free(workspace);
}
				

The following are the QuickC and C compiler compiling lines for the above C code: To create a Quick library from the C routine, the link line is as follows for QuickBasic 4.5: