The %m format can be used to format the current errno. It is non-standard but supported by other commonly used libcs like glibc and musl, so applications do rely on them.
Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de --- tools/include/nolibc/stdio.h | 7 +++++++ tools/testing/selftests/nolibc/nolibc-test.c | 18 ++++++++++++++++++ 2 files changed, 25 insertions(+)
diff --git a/tools/include/nolibc/stdio.h b/tools/include/nolibc/stdio.h index fb0417477759ee6c9663e84807c1d1067e735dec..02426682c34bcd82d9556036c6c3e73a6a5a3b4d 100644 --- a/tools/include/nolibc/stdio.h +++ b/tools/include/nolibc/stdio.h @@ -17,6 +17,8 @@ #include "string.h" #include "compiler.h"
+static const char *strerror(int errnum); + #ifndef EOF #define EOF (-1) #endif @@ -289,6 +291,11 @@ int __nolibc_printf(__nolibc_printf_cb cb, intptr_t state, size_t n, const char if (!outstr) outstr="(null)"; } +#ifndef NOLIBC_IGNORE_ERRNO + else if (c == 'm') { + outstr = strerror(errno); + } +#endif /* NOLIBC_IGNORE_ERRNO */ else if (c == '%') { /* queue it verbatim */ continue; diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 3e15a25ccddf5135db1f59bce1eefdff2ffe57f6..b7440a667db6b541a2548bdf5182bee0277100ed 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -1393,6 +1393,23 @@ static int test_scanf(void) return 0; }
+int test_strerror(void) +{ + char buf[100]; + ssize_t ret; + + memset(buf, 'A', sizeof(buf)); + + errno = EINVAL; + ret = snprintf(buf, sizeof(buf), "%m"); + if (is_nolibc) { + if (ret < 6 || memcmp(buf, "errno=", 6)) + return 1; + } + + return 0; +} + static int run_printf(int min, int max) { int test; @@ -1421,6 +1438,7 @@ static int run_printf(int min, int max) CASE_TEST(number_width); EXPECT_VFPRINTF(10, " 1", "%10d", 1); break; CASE_TEST(width_trunc); EXPECT_VFPRINTF(25, " ", "%25d", 1); break; CASE_TEST(scanf); EXPECT_ZR(1, test_scanf()); break; + CASE_TEST(strerror); EXPECT_ZR(1, test_strerror()); break; case __LINE__: return ret; /* must be last */ /* note: do not set any defaults so as to permit holes above */