From 4e0a64a7135b204f140058ed9f53299819db447e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C3=86var=20Arnfj=C3=B6r=C3=B0=20Bjarmason?= Date: Thu, 20 May 2021 13:05:45 +0200 Subject: [PATCH] trace2: refactor to avoid gcc warning under -O3 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Refactor tr2_dst_try_uds_connect() to avoid a gcc warning[1] that appears under -O3 (but not -O2). This makes the build pass under DEVELOPER=1 without needing a DEVOPTS=no-error. This can be reproduced with GCC Debian 8.3.0-6, but not e.g. with clang 7.0.1-8+deb10u2. We've had this warning since ee4512ed481 (trace2: create new combined trace facility, 2019-02-22). As noted in [2] this warning happens because the compiler doesn't assume that errno must be non-zero after a failed syscall. Let's work around by using the well-established "saved_errno" pattern, along with returning -1 ourselves instead of "errno". The caller can thus rely on our "errno" on failure. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61846 for a related bug report against GCC. 1. trace2/tr2_dst.c: In function ‘tr2_dst_get_trace_fd.part.5’: trace2/tr2_dst.c:296:10: warning: ‘fd’ may be used uninitialized in this function [-Wmaybe-uninitialized] dst->fd = fd; ~~~~~~~~^~~~ trace2/tr2_dst.c:229:6: note: ‘fd’ was declared here int fd; ^~ 2. https://lore.kernel.org/git/20200404142131.GA679473@coredump.intra.peff.net/ Signed-off-by: Ævar Arnfjörð Bjarmason Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- trace2/tr2_dst.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/trace2/tr2_dst.c b/trace2/tr2_dst.c index 5dda0ca1cd..0031476350 100644 --- a/trace2/tr2_dst.c +++ b/trace2/tr2_dst.c @@ -115,15 +115,16 @@ static int tr2_dst_try_uds_connect(const char *path, int sock_type, int *out_fd) fd = socket(AF_UNIX, sock_type, 0); if (fd == -1) - return errno; + return -1; sa.sun_family = AF_UNIX; strlcpy(sa.sun_path, path, sizeof(sa.sun_path)); if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) { - int e = errno; + int saved_errno = errno; close(fd); - return e; + errno = saved_errno; + return -1; } *out_fd = fd; @@ -138,7 +139,6 @@ static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst, { unsigned int uds_try = 0; int fd; - int e; const char *path = NULL; /* @@ -182,15 +182,13 @@ static int tr2_dst_try_unix_domain_socket(struct tr2_dst *dst, } if (uds_try & TR2_DST_UDS_TRY_STREAM) { - e = tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd); - if (!e) + if (!tr2_dst_try_uds_connect(path, SOCK_STREAM, &fd)) goto connected; - if (e != EPROTOTYPE) + if (errno != EPROTOTYPE) goto error; } if (uds_try & TR2_DST_UDS_TRY_DGRAM) { - e = tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd); - if (!e) + if (!tr2_dst_try_uds_connect(path, SOCK_DGRAM, &fd)) goto connected; } @@ -198,7 +196,7 @@ error: if (tr2_dst_want_warning()) warning("trace2: could not connect to socket '%s' for '%s' tracing: %s", path, tr2_sysenv_display_name(dst->sysenv_var), - strerror(e)); + strerror(errno)); tr2_dst_trace_disable(dst); return 0;