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#define FOO(a, b, c) bar(a, b, c) /* ... */ FOO(arg1, arg2, arg3); |
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*PRE01-EX2:* Macro parameters cannot be individually parenthesized when concatenating tokens using the {{##}} operator, converting macro parameters to strings using the {{#}} operator, or concatenating adjacent string literals. The {{JOIN()}} macro below concatenates both arguments to form a new token. The |
{{SHOWA()}} macro converts the single argument into a string literal, which is then concatenated with the adjacent string literal to form the format specification in the call to {{printf()}}. The {{SHOWB()}} macro is an improved version of {{SHOWA()}} that supports invocations of the form {{SHOWB(i%j)}}. It also eliminates the possibility of a format string vulnerability (see \[[FIO30-C. Exclude user input from format strings]]). |
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#define JOIN(a, b) (a ## b) #define SHOWSHOWA(a) printf(#a " = %d\n", a) #define SHOWB(b) printf("%s = %d\n", #b, b) |
See PRE05-A. Understand macro replacement when concatenating tokens for more information on using the ## operator to concatenate tokens.
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