National Instruments 320685D-01 Disabling Library Protection Errors for Functions

Chapter 1 LabWindows/CVI Compiler
© National Instruments Corporation 1-13 LabWindows/CVI Programmer Reference Manual
This macro could be useful in the following situation: LabWindows/CVI reports erroneous
run-time errors because you set a pointer to dynamic memory in a source module and you then
resize it in an object module. The following steps describe how this error occurs:
1. You declare a pointer in a source module you compile with debugging enabled. Y ou then
assign to the pointer an address that malloc or calloc returns:
AnyType *ptr;
ptr = malloc(N);
2. You reallocate the pointer in an object module so that it points to the same location in
memory as before. This might occur if you call the realloc function or free the pointer
and then reassign it to memory that you allocate with malloc:
ptr = realloc(ptr, M); /* M > N */
or
free(ptr);
ptr = malloc(M);
3. You use the same pointer in a source module you compile with debugging enabled. At
this point, LabWindows/CVI still expects the pointer to point to a block of memory of
the original size (N).
*(ptr+(M-1)) /* This generates a fatal run-time error, */
/* even though it is a legal expression. */
To prevent this error, use the DISABLE_RUNTIME_CHECKING macro to disable checking for
the pointer after you allocate memory for it in the source module:
ptr = malloc(N);
DISABLE_RUNTIME_CHECKING(ptr);
Disabling Library Protection Errors for Functions
You can disable or enable library protection errors by placing pragmas in the source code.
LabWindows/CVI ignores these pragmas when you compile wit hout deb uggin g info rmation,
that is, if the debugging level is None. For example, the following two pragmas enable and
disable library checking for all the function declarations that occur after the pragma within a
header or source file. The pragmas affect only the functions declared in the file in which the
pragmas occur. These pragmas do not affect nested include files.
#pragma EnableLibraryRuntimeChecking
#pragma DisableLibraryRuntimeChecking
The following pragmas enable and disable library checking for a particular function. You
must declare the function before the occurrence of the pragma.
#pragma EnableFunctionRuntimeChecking function
#pragma DisableFunctionRuntimeChecking function
00ProRef.book : 06chap01.fm Page 13 Monday, March 9, 1998 3:23 PM