Re: [for-next][PATCH 23/24] string.h: Add strncmp_prefix() helper macro

Andreas Schwab
2018-12-21T20:58:39Z

On Dez 21 2018, Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 21 Dec 2018 12:46:47 -0800
> Joe Perches <joe@perches.com> wrote:
>
>> > + * @str: The string to test
>> > + * @prefix: The string to see if @str starts with
>> > + *
>> > + * A common way to test a prefix of a string is to do:
>> > + * strncmp(str, prefix, sizeof(prefix) - 1)
>> > + *
>> > + * But this can lead to bugs due to typos, or if prefix is a pointer
>> > + * and not a constant. Instead use has_prefix().
>> > + *
>> > + * Returns: 0 if @str does not start with @prefix
>> > + strlen(@prefix) if @str does start with @prefix
>> > + */
>> > +#define has_prefix(str, prefix) \
>> > + ({ \
>> > + const char *____prefix____ = (const char *)(prefix); \
>> > + int ____len____ = strlen(____prefix____); \
>> > + strncmp(str, ____prefix____, ____len____) == 0 ? \
>> > + ____len____ : 0; \
>> > + })
>>
>> I think all the underscores are unnecessary and confusing.
>>
>
> Well, perhaps I can just remove the ending ones. I get paranoid with
> macro variables, and tend to over do it so that there's no question.

Why not make it an inline function?

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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