The arguments to a macro should must not include preprocessor directives, such as #define, #ifdef, and #include. Doing so is undefined behavior, according to subclause 6.10.3, paragraph 11, of the C Standard [ISO/IEC 9899:2011]:
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| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <string.h>
void func(const char *src) {
/* Validate the source string; calculate size */
char *dest;
/* malloc() destination string */
memcpy(dest, src,
#ifdef PLATFORM1
12
#else
24
#endif
);
/* ... */
);
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| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <string.h>
void func(const char *src) {
/* Validate the source string; calculate size */
char *dest;
/* malloc() destination string */
#ifdef PLATFORM1
memcpy(dest, src, 12);
#else
memcpy(dest, src, 24);
#endif
/* ... */
} |
Risk Assessment
Using Including preprocessor directives inside in macro arguments is undefined behavior.
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