This one makes my day.
A really good fix as it minimizes maintenance burden for checking
incoming patches for that pattern.
Reviewed-by: Stefan Beller <sbeller@xxxxxxxxxx>
On Tue, Nov 18, 2014 at 5:37 PM, Jeff King <peff@xxxxxxxx> wrote:
> It's common to use error() to return from a function, like:
>
> if (open(...) < 0)
> return error("open failed");
>
> Unfortunately this may clobber the errno from the open()
> call. So we often end up with code like this:
>
> if (open(...) < 0) {
> int saved_errno = errno;
> error("open failed");
> errno = saved_errno;
> return -1;
> }
>
> which is less nice. Let's teach error() to save and restore
> errno in each call, so that the original errno is preserved.
> This is slightly less efficient for callers which do not
> care, but error code paths are generally not performance
> critical anyway.
>
> Signed-off-by: Jeff King <peff@xxxxxxxx>
> ---
> It's pretty minor to just handle errno in the callers, but I feel like
> I've wanted this at least a dozen times, and it seems like it cannot
> possibly hurt (i.e., I imagine there are callers where we _should_ be
> doing the errno dance but have not realized it).
>
> usage.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/usage.c b/usage.c
> index ed14645..ee44d57 100644
> --- a/usage.c
> +++ b/usage.c
> @@ -142,10 +142,13 @@ void NORETURN die_errno(const char *fmt, ...)
> int error(const char *err, ...)
> {
> va_list params;
> + int saved_errno = errno;
>
> va_start(params, err);
> error_routine(err, params);
> va_end(params);
> +
> + errno = saved_errno;
> return -1;
> }
>
> --
> 2.1.2.596.g7379948
>
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