From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp62.i.mail.ru (smtp62.i.mail.ru [217.69.128.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dev.tarantool.org (Postfix) with ESMTPS id 392E74696C3 for ; Sat, 11 Apr 2020 01:28:13 +0300 (MSK) From: Alexander Turenko Date: Sat, 11 Apr 2020 01:28:07 +0300 Message-Id: <5f71273b0240cfc9cb1ee6f6473e30850650be25.1586557519.git.alexander.turenko@tarantool.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [Tarantool-patches] [PATCH] popen: fix 'may be clobbered' compiler warning List-Id: Tarantool development patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cyrill Gorcunov Cc: tarantool-patches@dev.tarantool.org I guess a compiler assumes that the code inside vfork may use the stack slot that corresponds the variable and so clobber it. The recent commit 07a07b3cc7b85375d20b3fc6ca1e5060304f337b ('popen: decouple logger fd from stderr') adds read from this variable after vfork() in the parent process. The warning is produced on RelWithDebInfo build with LTO enabled on GCC 9.2.0 (locally) and on GCC 8.3.0 (in CI). Part of #4031 --- We have -Werror enabled on some jobs in CI, so the warnings fails the CI status. See https://gitlab.com/tarantool/tarantool/-/jobs/506891936 I verified the build locally and in CI. https://github.com/tarantool/tarantool/tree/Totktonada/gh-4031-popen-fix-lto-build-full-ci src/lib/core/popen.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/src/lib/core/popen.c b/src/lib/core/popen.c index 5d0587e00..df7f797b9 100644 --- a/src/lib/core/popen.c +++ b/src/lib/core/popen.c @@ -784,10 +784,11 @@ struct popen_handle * popen_new(struct popen_opts *opts) { /* - * Without volatile compiler claims that - * handle might be clobbered from vfork. + * Without volatile compiler claims that those + * variables might be clobbered from vfork. */ struct popen_handle * volatile handle; + int volatile log_fd = -1; int pfd[POPEN_FLAG_FD_STDEND_BIT][2] = { {-1, -1}, {-1, -1}, {-1, -1}, @@ -853,7 +854,6 @@ popen_new(struct popen_opts *opts) * reached a file descriptor limit. */ int old_log_fd = log_get_fd(); - int log_fd = -1; if (old_log_fd >= 0) { log_fd = dup_not_std_streams(old_log_fd); if (log_fd < 0) -- 2.25.0