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The C99 printf() function is implemented as a variadic function. This non-compliant code example swaps its NULL terminated byte string and integer parameters with respect to how they were specified in the format string. Consequently, the integer is interpreted as a pointer to a NULL terminated byte string and dereferenced. This will likely cause the program to abnormally terminate. Note that the error_message pointer is likewise interpreted as an integer.

const char const *error_msg = "Error occurred";
/* ... */
printf("%s:%d", 15, error_msg);

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This compliant solution is formatted so that the specifiers are consistent with their parameters.

const char const *error_msg = "Error occurred";
/* ... */
printf("%d:%s", 15, error_msg);

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