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[35.187.50.168]) by smtp.gmail.com with ESMTPSA id 74sm3420669wmf.38.2018.02.23.14.17.17 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 23 Feb 2018 14:17:17 -0800 (PST) From: Junio C Hamano To: =?utf-8?Q?Ren=C3=A9?= Scharfe Cc: Jeff King , Git List , Johannes Schindelin Subject: Re: [PATCH] strbuf_read_file(): preserve errno across close() call References: <6b58885c-b0f6-1687-3f2d-4594aacff9ac@web.de> <20180223064952.GB19791@sigill.intra.peff.net> <20180223070053.GC19791@sigill.intra.peff.net> Date: Fri, 23 Feb 2018 14:17:17 -0800 In-Reply-To: (=?utf-8?Q?=22R?= =?utf-8?Q?en=C3=A9?= Scharfe"'s message of "Fri, 23 Feb 2018 22:00:24 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org René Scharfe writes: > +#define IGNORE_ERROR(expr) do { int e_ = errno; expr; errno = e_; } while (0) The macro certainly is a cute idea, but ... > @@ -391,7 +393,7 @@ ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint) > > if (got < 0) { > if (oldalloc == 0) > - strbuf_release(sb); > + IGNORE_ERROR(strbuf_release(sb)); > else > strbuf_setlen(sb, oldlen); > return -1; ... ideally, I would imagine that we wish we could write this hunk to something that expands to: if (got < 0) { do { int e_ = errno; if (oldalloc == 0) strbuf_release(sb); else strbuf_setlen(sb, oldlen); errno = e_; } while (0); return -1; no? That is (1) we do not want to rely too much on knowing that strbuf_setlen() is very thin and does not touch errno, and hence (2) we want to mark not just a single expr but a block as "we know we got an error and errno from that error is more precious than what we do in this block to clean thihngs up". Of course, a pair of macros #define IGNORE_ERROR_BEGIN do { int e_ = errno #define IGNORE_ERROR_END errno = e_; } while (0) is probably the only way to do so in C, and that is already too ugly to live, so we cannot achieve the ideal. So I dunno.. > @@ -617,9 +619,11 @@ ssize_t strbuf_read_file(struct strbuf *sb, const char *path, size_t hint) > if (fd < 0) > return -1; > len = strbuf_read(sb, fd, hint); > - close(fd); > - if (len < 0) > + if (len < 0) { > + IGNORE_ERROR(close(fd)); > return -1; > + } > + close(fd); > > return len; > }