From 9c6d78c26d7232483bcb6609825a225bae44cfe7 Mon Sep 17 00:00:00 2001 From: Gabriel Ravier Date: Fri, 31 Mar 2023 15:57:29 +0200 Subject: [PATCH] Fix vfprintf and derived functions not handling write errors (#798) The C standard states: > The fprintf function returns the number of characters transmitted, > or a negative value if an output or encoding error occurred or if > the implementation does not support a specified width length > modifier. - C Standard, 7.23.6.1.15. The fprintf function However, cosmopolitan fails to return a negative value in the case of an output error, meaning that a program such as: #include int main() { FILE *fp = fopen("/dev/full", "w"); setbuf(fp, NULL); printf("fprintf: %d\n", fprintf(fp, "test\n")); printf("fflush: %d\n", fflush(fp)); } will, under cosmopolitan, print that no error occured in either of the calls to fprintf and fflush. This patch fixes this, along with the associated GitHub issue, https://github.com/jart/cosmopolitan/issues/784 --- libc/stdio/vfprintf_unlocked.c | 2 +- test/libc/fmt/fprintf_test.c | 34 ++++++++++++++++++++++++++++++++++ test/libc/fmt/test.mk | 3 +++ 3 files changed, 38 insertions(+), 1 deletion(-) create mode 100644 test/libc/fmt/fprintf_test.c diff --git a/libc/stdio/vfprintf_unlocked.c b/libc/stdio/vfprintf_unlocked.c index 940e3e351..1e20f7831 100644 --- a/libc/stdio/vfprintf_unlocked.c +++ b/libc/stdio/vfprintf_unlocked.c @@ -44,7 +44,7 @@ static int vfprintfputchar(const char *s, struct state *t, size_t n) { } else { rc = 0; } - return 0; + return rc; } /** diff --git a/test/libc/fmt/fprintf_test.c b/test/libc/fmt/fprintf_test.c new file mode 100644 index 000000000..d3e590c97 --- /dev/null +++ b/test/libc/fmt/fprintf_test.c @@ -0,0 +1,34 @@ +/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│ +│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│ +╞══════════════════════════════════════════════════════════════════════════════╡ +│ Copyright 2023 Gabriel Ravier │ +│ │ +│ Permission to use, copy, modify, and/or distribute this software for │ +│ any purpose with or without fee is hereby granted, provided that the │ +│ above copyright notice and this permission notice appear in all copies. │ +│ │ +│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │ +│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │ +│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │ +│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │ +│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │ +│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │ +│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │ +│ PERFORMANCE OF THIS SOFTWARE. │ +╚─────────────────────────────────────────────────────────────────────────────*/ +#include "libc/dce.h" +#include "libc/stdio/stdio.h" +#include "libc/testlib/testlib.h" + +TEST(fprintf, testWriteError) { + // Only Linux, NetBSD and FreeBSD are known to have /dev/full + if (!IsLinux() && !IsNetbsd() && !IsFreebsd()) return; + + FILE *fp = fopen("/dev/full", "w"); + ASSERT_NE(fp, NULL); + + setbuf(fp, NULL); + ASSERT_LT(fprintf(fp, "test"), 0); + + ASSERT_EQ(fclose(fp), 0); +} diff --git a/test/libc/fmt/test.mk b/test/libc/fmt/test.mk index 3c76b56ea..8ed240936 100644 --- a/test/libc/fmt/test.mk +++ b/test/libc/fmt/test.mk @@ -55,6 +55,9 @@ $(TEST_LIBC_FMT_OBJS): private \ DEFAULT_CCFLAGS += \ -fno-builtin +o/$(MODE)/test/libc/fmt/fprintf_test.com.runs: \ + private .UNVEIL += w:/dev/full + .PHONY: o/$(MODE)/test/libc/fmt o/$(MODE)/test/libc/fmt: \ $(TEST_LIBC_FMT_BINS) \