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The arguments to a macro should not include preprocessor directives such as {{\#define}}, {{\#ifdef}}, and {{\#include}}. Doing so is [undefined behavior|BB. Definitions#undefined behavior] according to section 6.10.3.1, paragraph 11 of the C99 standard \[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\]: |
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<blockquote><p>The sequence of preprocessing tokens bounded by the outside-most matching parentheses forms the list of arguments for the function-like macro. |
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The individual arguments within the list are separated by comma preprocessing tokens, but comma preprocessing tokens between matching inner parentheses do not separate arguments. |
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The scope of this rule includes using preprocessor directives in arguments to a function where it is unknown whether or not the function is implemented using a macro. For example, standard library functions such as memcpy(), printf(), and assert() may be implemented as
<strong>If there are sequences of preprocessing tokens within the list of arguments that would otherwise act as preprocessing directives, the behavior is undefined.</strong></p></blockquote>The scope of this rule includes using preprocessor directives in arguments to a function where it is unknown whether or not the function is implemented using a macro. For example, standard library functions such as {{memcpy()}}, {{printf()}}, and {{assert()}} may be implemented as macros. |
Noncompliant Code Example
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\[[GCC Bugs|http://gcc.gnu.org/bugs.html#nonbugs_c]\] "Non-bugs" \[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\] Section 6.10.3.111, "MacroArgument replacement"substitution," paragraph 11 |