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