TNS/R Native Application Migration Guide

C and C++ Migration Tasks
TNS/R Native Application Migration Guide—523745-001
3-7
Replacing Obsolete External Function Declarations
•
Ensure that the formal and actual parameters of pointer types are matched. The
TNS C compiler issues the following warning message if pointers do not match:
Warning 30: pointers do not point to same type of object
For example:
int func1(short *);
In the 16-bit data model and the large-memory model, you can pass to func1 a
pointer of type short or int and get correct results. In the 32-bit data model, you
can pass to func1 only a pointer of type short; a pointer of type int generates
incorrect results.
Parameter mismatch is most often an issue for Guardian system procedures and
external TAL and pTAL procedures.
•
Ensure that literals do not cause type mismatches, as illustrated in this example:
#include <cextdecs(MONITORCPUS)>
...
short get_cpu_number;
MONITORCPUS(0x8000 >> get_cpu_number);
In the 32-bit data model, if get_cpu_number is equal to zero, an arithmetic
overflow occurs because the compiler generates code to convert an unsigned
32-bit integer to a 16-bit signed integer. Declarations in the cextdecs header file
do not use the type unsigned short.
•
Avoid using the type int in your program, if possible. Use type long or short
instead. However, if you want to keep your program data-model independent, you
cannot avoid using type int completely. For example, C library calls, bit fields,
TCP/IP sockets library functions, and Guardian system procedures might require
type int.
Replacing Obsolete External Function
Declarations
External function declarations declare functions not written in the C language. D-series
TNS C compilers recognize correctly but issue warnings for C-series external function
declaration syntax with D-series replacements. The native compilers do not recognize
the C-series syntax. If you use FUNCTION pragma syntax or declarations with
_language name keywords (such as _tal and _c), no changes are required. See the
C/C++ Programmer’s Guide for details.