Re: [PATCH v2 2/3] Introduce a function to run regexec() on non-NUL-terminated buffers

[Jeff King <peff@peff.net>]

On Thu, Sep 08, 2016 at 09:31:11AM +0200, Johannes Schindelin wrote:

> diff --git a/git-compat-util.h b/git-compat-util.h
> index db89ba7..19128b3 100644
> --- a/git-compat-util.h
> +++ b/git-compat-util.h
> @@ -965,6 +965,27 @@ void git_qsort(void *base, size_t nmemb, size_t size,
>  #define qsort git_qsort
>  #endif
>  
> +static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size,
> +			      size_t nmatch, regmatch_t pmatch[], int eflags)
> +{
> +#ifdef REG_STARTEND
> +	assert(nmatch > 0 && pmatch);
> +	pmatch[0].rm_so = 0;
> +	pmatch[0].rm_eo = size;
> +	return regexec(preg, buf, nmatch, pmatch, eflags | REG_STARTEND);
> +#else
> +	char *buf2 = xmalloc(size + 1);
> +	int ret;
> +
> +	memcpy(buf2, buf, size);
> +	buf2[size] = '\0';

I mentioned elsewhere that I'd prefer we just push people into using
compat/regex if they don't have REG_STARTEND. But if we _do_ keep this
fallback, note that the above has a buffer overflow (think what happens
when "size" is the maximum value for a size_t).  You can avoid it by
using xmallocz().

-Peff