libc: minimal: add strerror and strerror_r function
Add simple strerror() and strerror_r() implementations.
Fixes #46099
Signed-off-by: Christopher Friedt <cfriedt@fb.com>
diff --git a/lib/libc/Kconfig b/lib/libc/Kconfig
index ed06e7c..d4124e1 100644
--- a/lib/libc/Kconfig
+++ b/lib/libc/Kconfig
@@ -217,6 +217,17 @@
In order to make use of the non-reentrant gmtime(), it is necessary
to set CONFIG_MINIMAL_LIBC_NON_REENTRANT_FUNCTIONS=y.
+config MINIMAL_LIBC_STRING_ERROR_TABLE
+ bool "String error table for strerror() and strerror_r()"
+ help
+ Select this option to ensure that streror(), strerror_r()
+ produce strings corresponding to the descriptions in errno.h.
+
+ The string error table can add ~2kiB to ROM. As such, it is
+ disabled by default. In this case, strerror() and strerror_r()
+ symbols are still present, but the functions produce an empty
+ string.
+
endif # MINIMAL_LIBC
config STDOUT_CONSOLE
diff --git a/lib/libc/minimal/CMakeLists.txt b/lib/libc/minimal/CMakeLists.txt
index 6fd36e7..6d857fe 100644
--- a/lib/libc/minimal/CMakeLists.txt
+++ b/lib/libc/minimal/CMakeLists.txt
@@ -3,6 +3,10 @@
zephyr_system_include_directories(include)
zephyr_library()
+
+set(GEN_DIR ${ZEPHYR_BINARY_DIR}/include/generated)
+set(STRERROR_TABLE_H ${GEN_DIR}/libc/minimal/strerror_table.h)
+
zephyr_library_sources(
source/stdlib/abort.c
source/stdlib/atoi.c
@@ -14,6 +18,7 @@
source/stdlib/bsearch.c
source/stdlib/exit.c
source/stdlib/qsort.c
+ source/string/strerror.c
source/string/strncasecmp.c
source/string/strstr.c
source/string/string.c
@@ -23,6 +28,7 @@
source/stdout/fprintf.c
source/math/sqrtf.c
source/math/sqrt.c
+ ${STRERROR_TABLE_H}
)
if(CONFIG_MINIMAL_LIBC_TIME)
@@ -31,3 +37,14 @@
endif()
zephyr_library_sources_ifdef(CONFIG_MINIMAL_LIBC_RAND source/stdlib/rand.c)
+
+add_custom_command(
+ OUTPUT ${STRERROR_TABLE_H}
+ COMMAND
+ ${PYTHON_EXECUTABLE}
+ ${ZEPHYR_BASE}/scripts/gen_strerror_table.py
+ -i include/errno.h
+ -o ${STRERROR_TABLE_H}
+ DEPENDS include/errno.h
+ WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+)
diff --git a/lib/libc/minimal/include/string.h b/lib/libc/minimal/include/string.h
index ecf834d..35052c0 100644
--- a/lib/libc/minimal/include/string.h
+++ b/lib/libc/minimal/include/string.h
@@ -17,6 +17,8 @@
#endif
extern char *strcpy(char *ZRESTRICT d, const char *ZRESTRICT s);
+extern char *strerror(int errnum);
+extern int strerror_r(int errnum, char *strerrbuf, size_t buflen);
extern char *strncpy(char *ZRESTRICT d, const char *ZRESTRICT s,
size_t n);
extern char *strchr(const char *s, int c);
diff --git a/lib/libc/minimal/source/string/strerror.c b/lib/libc/minimal/source/string/strerror.c
new file mode 100644
index 0000000..ae2c02f
--- /dev/null
+++ b/lib/libc/minimal/source/string/strerror.c
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2022 Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <errno.h>
+#include <string.h>
+
+#include <zephyr/sys/util.h>
+
+/*
+ * See scripts/gen_strerror_table.py
+ *
+ * #define sys_nerr N
+ * const char *const sys_errlist[sys_nerr];
+ * const uint8_t sys_errlen[sys_nerr];
+ */
+#include "libc/minimal/strerror_table.h"
+
+/*
+ * See https://pubs.opengroup.org/onlinepubs/9699919799/functions/strerror.html
+ */
+char *strerror(int errnum)
+{
+ if (IS_ENABLED(CONFIG_MINIMAL_LIBC_STRING_ERROR_TABLE) &&
+ errnum >= 0 && errnum < sys_nerr) {
+ return (char *)sys_errlist[errnum];
+ }
+
+ return "";
+}
+
+/*
+ * See
+ * https://pubs.opengroup.org/onlinepubs/9699919799/functions/strerror_r.html
+ */
+int strerror_r(int errnum, char *strerrbuf, size_t buflen)
+{
+ const char *msg;
+ size_t msg_len;
+
+ if (errnum >= 0 && errnum < sys_nerr) {
+ if (IS_ENABLED(CONFIG_MINIMAL_LIBC_STRING_ERROR_TABLE)) {
+ msg = sys_errlist[errnum];
+ msg_len = sys_errlen[errnum];
+ } else {
+ msg = "";
+ msg_len = 1;
+ }
+
+ if (buflen < msg_len) {
+ return ERANGE;
+ }
+
+ strncpy(strerrbuf, msg, msg_len);
+ }
+
+ if (errnum < 0 || errnum >= sys_nerr) {
+ return EINVAL;
+ }
+
+ return 0;
+}
diff --git a/scripts/gen_strerror_table.py b/scripts/gen_strerror_table.py
new file mode 100755
index 0000000..4e04d79
--- /dev/null
+++ b/scripts/gen_strerror_table.py
@@ -0,0 +1,107 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2022 Meta
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import argparse
+import os
+import re
+
+
+def front_matter(sys_nerr):
+ return f'''
+/*
+ * This file generated by {__file__}
+ */
+
+#include <errno.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <zephyr/sys/util.h>
+
+#define sys_nerr {sys_nerr}'''
+
+
+def gen_strerror_table(input, output):
+ with open(input, 'r') as inf:
+
+ highest_errno = 0
+ symbols = []
+ msgs = {}
+
+ for line in inf.readlines():
+ # Select items of the form below (note: ERRNO is numeric)
+ # #define SYMBOL ERRNO /**< MSG */
+ pat = r'^#define[\s]+(E[A-Z_]*)[\s]+([1-9][0-9]*)[\s]+/\*\*<[\s]+(.*)[\s]+\*/[\s]*$'
+ match = re.match(pat, line)
+
+ if not match:
+ continue
+
+ symbol = match[1]
+ errno = int(match[2])
+ msg = match[3]
+
+ symbols.append(symbol)
+ msgs[symbol] = msg
+
+ highest_errno = max(int(errno), highest_errno)
+
+ try:
+ os.makedirs(os.path.dirname(output))
+ except BaseException:
+ # directory already present
+ pass
+
+ with open(output, 'w') as outf:
+
+ print(front_matter(highest_errno + 1), file=outf)
+
+ # Generate string table
+ print(
+ f'static const char *const sys_errlist[sys_nerr] = {{', file=outf)
+ print('[0] = "Success",', file=outf)
+ for symbol in symbols:
+ print(f'[{symbol}] = "{msgs[symbol]}",', file=outf)
+
+ print('};', file=outf)
+
+ # Generate string lengths (includes trailing '\0')
+ print(
+ f'static const uint8_t sys_errlen[sys_nerr] = {{', file=outf)
+ print('[0] = 8,', file=outf)
+ for symbol in symbols:
+ print(f'[{symbol}] = {len(msgs[symbol]) + 1},', file=outf)
+
+ print('};', file=outf)
+
+
+def parse_args():
+ parser = argparse.ArgumentParser()
+ parser.add_argument(
+ '-i',
+ '--input',
+ dest='input',
+ required=True,
+ help='input file (e.g. lib/libc/minimal/include/errno.h)')
+ parser.add_argument(
+ '-o',
+ '--output',
+ dest='output',
+ required=True,
+ help='output file (e.g. build/zephyr/misc/generated/libc/minimal/strerror_table.h)')
+
+ args = parser.parse_args()
+
+ return args
+
+
+def main():
+ args = parse_args()
+ gen_strerror_table(args.input, args.output)
+
+
+if __name__ == '__main__':
+ main()
