Re: [PATCH] git-log: detect dup and fdopen failure

> On Jun 27, 2007, at 09:02, Jim Meyering wrote:
>> -	if (!use_stdout)
>> -		realstdout = fdopen(dup(1), "w");
>> +	if (!use_stdout) {
>> +		int fd = dup(1);
>> +		if (fd < 0 || (realstdout = fdopen(fd, "w")) == NULL)
>> +			die("failed to duplicate standard output: %s",
>> +			    strerror(errno));
>> +	}
>
> This makes the code unreadable! A great way to ruin
> perfectly fine code is to add tons of error checking.
> The error checking is likely wrong (detects non-errors,
> or fails to detect real ones), and for sure makes code
> untestable  and unreadable.
>
> If we really case about catching such errors, write
> the code as:
> 	if (!use_stdout)
> 		realstdout = xfdopen(dup(1), "w");

> where xfdopen is a wrapper around fdopen that dies in
> case of an error. This follows a practice we use elsewhere,
> and only adds one character to the code and only affects
> readability very slightly.
>
>> Without this, if you ever run out of file descriptors, dup will
>> fail (silently), fdopen will return NULL, and fprintf will
>> try to dereference NULL (i.e., usually segfault).
>
> As it is unlikely the failure mode will ever occur in practice,
> any way of aborting is fine. Even SIGSEGV would do: it would be
> trivial to find that we were leaking file descriptors or are out
> of memory. Oh, wait, that means we don't need any checking code
> at all...