From: Jonathan Nieder Date: Tue, 28 Apr 2015 20:42:13 GMT Subject: Re: [PATCH v5 1/5] setup: add gentle version of read_gitfile Message-ID: <20150428204213.GO5467@google.com> In-Reply-To: <20150428203645.GA11473@peff.net> Jeff King wrote: > But the NULL does not carry the information about _which_ error, and > Erik is suggesting that the caller may need to change behavior based on > that information. IOW, his current patch (return NULL and set the > specific integer code in a variable) allows this, but switching the > integer code out for a human-readable strbuf does not. Right. Two ways to handle that are: - two out parameters: an integer code and a human-readable string, or - an integer code returned using the ERR_PTR method and a human-readable string out parameter The point I was trying to make clear is that the human-readable error message and the integer to affect control flow have different purposes and are not tightly related except in that they are produced at the same time. Using an integer to convey the human-readable error message (like errno does) unnecessarily forces the message to be more vague (by not being parameterized, and by always using the same error message for the same integer error).