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Avoid potential undesirable effects caused by macros 

The macros provided by this library would expand to an unguarded
conditional that could have potential unwanted consequences. Consider
the following example:

    dynstr_append_or_ret_null(&d, "example");
    else
    {
        /* This is unexpectedly working. */
    }

The example above would expand to:

    if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return false;
    else
    {
        /* This is unexpectedly working. */
    }

Which is valid C yet allows possibly unexpected behaviour. The solution
is then to enclose these conditions into a `do while (0)` statement.
This commit is contained in:
Xavier Del Campo Romero 2020-09-03 14:57:05 +02:00
parent 9b85c4beaa
commit 4c7bfbf87f
1 changed files with 8 additions and 4 deletions
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12
include/dynstr.h
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@ -30,12 +30,14 @@
/**
* Convenience macro that calls dynstr_append and returns NULL if failed.
*/
#define dynstr_append_or_ret_null(...) if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return NULL
#define dynstr_append_or_ret_null(...) \
do {if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return NULL;} while (0)
/**
* Convenience macro that calls dynstr_append and returns false if failed.
*/
#define dynstr_append_or_ret_false(...) if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return false
#define dynstr_append_or_ret_false(...) \
do {if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return false;} while (0)
/**
* Convenience macro that calls dynstr_append and returns its error code if failed.
@ -45,12 +47,14 @@
/**
* Convenience macro that calls dynstr_append and returns zero if failed.
*/
#define dynstr_append_or_ret_zero(...) if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return 0
#define dynstr_append_or_ret_zero(...) \
do {if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return 0;} while (0)
/**
* Convenience macro that calls dynstr_append and returns one if failed.
*/
#define dynstr_append_or_ret_nonzero(...) if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return 1
#define dynstr_append_or_ret_nonzero(...) \
do {if (dynstr_append(__VA_ARGS__) != DYNSTR_OK) return 1;} while (0)
/**
* Dynamic string type used for this library.