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From 9c95d8dda42de288a57638a44dd5ea967469063d Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
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Date: Fri, 7 Oct 2022 12:28:31 +0200
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Subject: [PATCH] basic: add STRERROR() wrapper for strerror_r()
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(cherry picked from commit 2c5d05b3cd986568105d67891e4010b868dea24f)
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Related: #2155520
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---
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src/basic/util.h | 10 ++++++++++
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src/test/test-util.c | 40 ++++++++++++++++++++++++++++++++++++++++
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2 files changed, 50 insertions(+)
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diff --git a/src/basic/util.h b/src/basic/util.h
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index 76b76d7e91..195f02cf5f 100644
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--- a/src/basic/util.h
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+++ b/src/basic/util.h
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@@ -153,6 +153,16 @@ static inline void _reset_errno_(int *saved_errno) {
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errno = *saved_errno;
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}
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+/* strerror(3) says that glibc uses a maximum length of 1024 bytes. */
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+#define ERRNO_BUF_LEN 1024
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+
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+/* Note: the lifetime of the compound literal is the immediately surrounding block,
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+ * see C11 §6.5.2.5, and
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+ * https://stackoverflow.com/questions/34880638/compound-literal-lifetime-and-if-blocks
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+ *
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+ * Note that we use the GNU variant of strerror_r() here. */
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+#define STRERROR(errnum) strerror_r(abs(errnum), (char[ERRNO_BUF_LEN]){}, ERRNO_BUF_LEN)
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+
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#define PROTECT_ERRNO _cleanup_(_reset_errno_) __attribute__((unused)) int _saved_errno_ = errno
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#define UNPROTECT_ERRNO \
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diff --git a/src/test/test-util.c b/src/test/test-util.c
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index df60d89115..c93eaf7fc6 100644
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--- a/src/test/test-util.c
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+++ b/src/test/test-util.c
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@@ -12,6 +12,7 @@
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#include "process-util.h"
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#include "raw-clone.h"
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#include "rm-rf.h"
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+#include "stdio-util.h"
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#include "string-util.h"
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#include "util.h"
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@@ -321,6 +322,42 @@ static void test_system_tasks_max_scale(void) {
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assert_se(system_tasks_max_scale(UINT64_MAX/4, UINT64_MAX) == UINT64_MAX);
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}
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+static void test_strerror_not_threadsafe(void) {
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+ /* Just check that strerror really is not thread-safe. */
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+ log_info("strerror(%d) → %s", 200, strerror(200));
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+ log_info("strerror(%d) → %s", 201, strerror(201));
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+ log_info("strerror(%d) → %s", INT_MAX, strerror(INT_MAX));
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+
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+ log_info("strerror(%d), strerror(%d) → %p, %p", 200, 201, strerror(200), strerror(201));
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+
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+ /* This call is not allowed, because the first returned string becomes invalid when
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+ * we call strerror the second time:
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+ *
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+ * log_info("strerror(%d), strerror(%d) → %s, %s", 200, 201, strerror(200), strerror(201));
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+ */
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+}
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+
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+static void test_STRERROR(void) {
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+ /* Just check that STRERROR really is thread-safe. */
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+ log_info("STRERROR(%d) → %s", 200, STRERROR(200));
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+ log_info("STRERROR(%d) → %s", 201, STRERROR(201));
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+ log_info("STRERROR(%d), STRERROR(%d) → %s, %s", 200, 201, STRERROR(200), STRERROR(201));
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+
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+ const char *a = STRERROR(200), *b = STRERROR(201);
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+ assert_se(strstr(a, "200"));
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+ assert_se(strstr(b, "201"));
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+
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+ /* Check with negative values */
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+ assert_se(streq(a, STRERROR(-200)));
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+ assert_se(streq(b, STRERROR(-201)));
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+
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+ const char *c = STRERROR(INT_MAX);
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+ char buf[DECIMAL_STR_MAX(int)];
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+ xsprintf(buf, "%d", INT_MAX); /* INT_MAX is hexadecimal, use printf to convert to decimal */
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+ log_info("STRERROR(%d) → %s", INT_MAX, c);
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+ assert_se(strstr(c, buf));
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+}
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+
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int main(int argc, char *argv[]) {
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log_parse_environment();
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log_open();
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@@ -340,5 +377,8 @@ int main(int argc, char *argv[]) {
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test_system_tasks_max();
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test_system_tasks_max_scale();
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+ test_strerror_not_threadsafe();
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+ test_STRERROR();
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+
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return 0;
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}
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