libc: minimal: errno.h, strerror to common, strerror_r to posix

The strerror_r() function is POSIX. It's not part of ISO C. Moreover, the versions available in both Newlib and Picolibc do not seem to comply with the POSIX specification OOTB. Moving this function to lib/posix ensures that Zephyr applications have a consistent implementation of the POSIX API. Signed-off-by: Christopher Friedt <[email protected]>
zephyrproject-rtos · Jan 13, 2024 · 7d7ac6d · 7d7ac6d
1 parent ae0ad38
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diff --git a/doc/develop/languages/c/common_libc.rst b/doc/develop/languages/c/common_libc.rst
@@ -45,3 +45,27 @@ The standard dynamic memory management interface functions implemented by
 the common C library are thread safe and may be simultaneously called by
 multiple threads. These functions are implemented in
 :file:`lib/libc/common/source/stdlib/malloc.c`.
+
+Error numbers
+*************
+
+Error numbers are used throughout Zephyr APIs to signal error conditions as
+return values from functions. They are typically returned as the negative value
+of the integer literals defined in this section, and are defined in the
+:file:`errno.h` header file.
+
+A subset of the error numbers defined in the `POSIX errno.h specification`_ and
+other de-facto standard sources have been added to the common libc resources.
+
+A conscious effort is made in Zephyr to keep the values of the common libc
+error numbers consistent with the different implementations of the C standard
+libraries supported by Zephyr. The minimal libc :file:`errno.h` is checked
+against that of the :ref:`Newlib <c_library_newlib>` to ensure that the error
+numbers are kept aligned.
+
+Below is a list of the error number definitions. For the actual numeric values
+please refer to :file:`lib/libc/common/include/errno.h`.
+
+.. doxygengroup:: system_errno
+
+.. _`POSIX errno.h specification`: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
diff --git a/doc/develop/languages/c/minimal_libc.rst b/doc/develop/languages/c/minimal_libc.rst
@@ -40,28 +40,3 @@ Dynamic Memory Management
 The minimal libc uses the malloc api family implementation provided by the
 :ref:`common C library <c_library_common>`, which itself is built upon the
 :ref:`kernel memory heap API <heap_v2>`.
-
-Error numbers
-*************
-
-Error numbers are used throughout Zephyr APIs to signal error conditions as
-return values from functions. They are typically returned as the negative value
-of the integer literals defined in this section, and are defined in the
-:file:`errno.h` header file.
-
-A subset of the error numbers defined in the `POSIX errno.h specification`_ and
-other de-facto standard sources have been added to the minimal libc.
-
-A conscious effort is made in Zephyr to keep the values of the minimal libc
-error numbers consistent with the different implementations of the C standard
-libraries supported by Zephyr. The minimal libc :file:`errno.h` is checked
-against that of the :ref:`Newlib <c_library_newlib>` to ensure that the error
-numbers are kept aligned.
-
-Below is a list of the error number definitions. For the actual numeric values
-please refer to `errno.h`_.
-
-.. doxygengroup:: system_errno
-
-.. _`POSIX errno.h specification`: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
-.. _`errno.h`: https://github.com/zephyrproject-rtos/zephyr/blob/main/lib/libc/minimal/include/errno.h
diff --git a/doc/zephyr.doxyfile.in b/doc/zephyr.doxyfile.in
@@ -924,6 +924,7 @@ INPUT                  = @ZEPHYR_BASE@/doc/_doxygen/mainpage.md \
                          @ZEPHYR_BASE@/doc/_doxygen/groups.dox \
                          @ZEPHYR_BASE@/kernel/include/kernel_arch_interface.h \
                          @ZEPHYR_BASE@/include/ \
+                         @ZEPHYR_BASE@/lib/libc/common/include/ \
                          @ZEPHYR_BASE@/lib/libc/minimal/include/ \
                          @ZEPHYR_BASE@/subsys/testsuite/include/ \
                          @ZEPHYR_BASE@/subsys/testsuite/ztest/include/

diff --git a/include/zephyr/sys/errno_private.h b/include/zephyr/sys/errno_private.h
@@ -20,6 +20,8 @@ extern "C" {
 #ifdef CONFIG_LIBC_ERRNO
 #include <errno.h>
 
+extern int __thread errno;
+
 static inline int *z_errno(void)
 {
 	return &errno;

diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
@@ -4,9 +4,7 @@
 add_compile_options($<TARGET_PROPERTY:compiler,warning_shadow_variables>)
 
 add_subdirectory(crc)
-if(NOT CONFIG_EXTERNAL_LIBC)
 add_subdirectory(libc)
-endif()
 if(NOT CONFIG_NATIVE_LIBC)
 add_subdirectory(posix)
 endif()

diff --git a/lib/libc/Kconfig b/lib/libc/Kconfig
@@ -74,6 +74,7 @@ config MINIMAL_LIBC
 	imply COMPILER_FREESTANDING
 	select COMMON_LIBC_ABORT
 	select COMMON_LIBC_STRNLEN
+	select COMMON_LIBC_STRERROR
 	help
 	  Build with minimal C library.
 
@@ -86,6 +87,7 @@ config PICOLIBC
 	imply COMMON_LIBC_MALLOC
 	depends on !NATIVE_APPLICATION
 	depends on PICOLIBC_SUPPORTED
+	select COMMON_LIBC_STRERROR
 	help
 	  Build with picolibc library. The picolibc library is built as
 	  a module if PICOLIBC_MODULE is set, otherwise picolibc is
@@ -97,6 +99,7 @@ config NEWLIB_LIBC
 	depends on !NATIVE_APPLICATION
 	depends on NEWLIB_LIBC_SUPPORTED
 	select NEED_LIBC_MEM_PARTITION
+	select COMMON_LIBC_STRERROR
 	help
 	  Build with newlib library. The newlib library is expected to be
 	  part of the SDK in this case.

diff --git a/lib/libc/common/CMakeLists.txt b/lib/libc/common/CMakeLists.txt
@@ -2,12 +2,19 @@
 
 zephyr_system_include_directories(include)
 
+set(GEN_DIR ${ZEPHYR_BINARY_DIR}/include/generated)
+set(STRERROR_TABLE_H ${GEN_DIR}/libc/common/strerror_table.h)
+
 zephyr_library()
 zephyr_library_property(ALLOW_EMPTY TRUE)
 zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_ABORT source/stdlib/abort.c)
 zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_TIME source/time/time.c)
 zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_MALLOC source/stdlib/malloc.c)
 zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_STRNLEN source/string/strnlen.c)
+zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_STRERROR
+    ${STRERROR_TABLE_H}
+    source/string/strerror.c
+    )
 zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_THRD
     source/thrd/cnd.c
     source/thrd/mtx.c
@@ -18,3 +25,14 @@ zephyr_library_sources_ifdef(CONFIG_COMMON_LIBC_THRD
 
 # Prevent compiler from optimizing calloc into an infinite recursive call
 zephyr_library_compile_options($<TARGET_PROPERTY:compiler,no_builtin_malloc>)
+
+add_custom_command(
+  OUTPUT ${STRERROR_TABLE_H}
+  COMMAND
+  ${PYTHON_EXECUTABLE}
+  ${ZEPHYR_BASE}/scripts/build/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/common/Kconfig b/lib/libc/common/Kconfig
@@ -68,6 +68,22 @@ config COMMON_LIBC_STRNLEN
 	help
 	  common implementation of strnlen().
 
+config COMMON_LIBC_STRERROR
+	bool "Common C library strerror"
+	default y
+	help
+	  common implementation of strerror().
+
+config COMMON_LIBC_STRING_ERROR_TABLE
+	bool "String error table for strerror()"
+	depends on COMMON_LIBC_STRERROR
+	help
+	  Select this option to ensure that strerror() produces 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() is still present but it produces an empty string.
+
 config COMMON_LIBC_THRD
 	bool "C11 <threads.h> API support"
 	depends on DYNAMIC_THREAD

diff --git a/lib/libc/minimal/include/errno.h → lib/libc/common/include/errno.h b/lib/libc/minimal/include/errno.h → lib/libc/common/include/errno.h
@@ -17,8 +17,8 @@
  * @brief System error numbers
  */
 
-#ifndef ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_ERRNO_H_
-#define ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_ERRNO_H_
+#ifndef ZEPHYR_LIB_LIBC_COMMON_INCLUDE_ERRNO_H_
+#define ZEPHYR_LIB_LIBC_COMMON_INCLUDE_ERRNO_H_
 
 /**
  * @brief System error numbers
@@ -127,4 +127,4 @@ extern "C" {
 }
 #endif
 
-#endif /* ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_ERRNO_H_ */
+#endif /* ZEPHYR_LIB_LIBC_COMMON_INCLUDE_ERRNO_H_ */
diff --git a/lib/libc/common/source/string/strerror.c b/lib/libc/common/source/string/strerror.c
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2022 Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <errno.h>
+#include <string.h>
+
+#include <zephyr/sys/util.h>
+#include <zephyr/toolchain.h>
+
+/*
+ * See scripts/build/gen_strerror_table.py
+ *
+ * #define sys_nerr N
+ * const char *const sys_errlist[sys_nerr];
+ * const uint8_t sys_errlen[sys_nerr];
+ */
+#define __sys_errlist_declare
+#include "libc/common/strerror_table.h"
+
+char *strerror(int errnum)
+{
+	if (IS_ENABLED(CONFIG_COMMON_LIBC_STRING_ERROR_TABLE) && errnum >= 0 && errnum < sys_nerr) {
+		return (char *)sys_errlist[errnum];
+	}
+
+	return (char *) "";
+}
diff --git a/lib/libc/minimal/CMakeLists.txt b/lib/libc/minimal/CMakeLists.txt
@@ -4,9 +4,6 @@ zephyr_system_include_directories(include)
 
 zephyr_library()
 
-set(GEN_DIR ${ZEPHYR_BINARY_DIR}/include/generated)
-set(STRERROR_TABLE_H ${GEN_DIR}/libc/minimal/strerror_table.h)
-
 zephyr_library_compile_options($<TARGET_PROPERTY:compiler,no_builtin>)
 
 zephyr_library_sources(
@@ -18,7 +15,6 @@ zephyr_library_sources(
   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
@@ -28,22 +24,10 @@ zephyr_library_sources(
   source/stdout/fprintf.c
   source/math/sqrtf.c
   source/math/sqrt.c
-  ${STRERROR_TABLE_H}
 )
 
 if(CONFIG_MINIMAL_LIBC_TIME)
   zephyr_library_sources(source/time/gmtime.c)
 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/build/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/Kconfig b/lib/libc/minimal/Kconfig
@@ -90,14 +90,11 @@ config MINIMAL_LIBC_TIME
 	  to set CONFIG_MINIMAL_LIBC_NON_REENTRANT_FUNCTIONS=y.
 
 config MINIMAL_LIBC_STRING_ERROR_TABLE
-	bool "String error table for strerror() and strerror_r()"
+	bool "String error table for strerror() [DEPRECATED]"
+	select DEPRECATED
+	select COMMON_LIBC_STRING_ERROR_TABLE
 	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.
+	  This option is deprecated. Use CONFIG_COMMON_LIBC_STRING_ERROR_TABLE
+	  instead.
 
 endif # MINIMAL_LIBC
diff --git a/lib/libc/minimal/include/string.h b/lib/libc/minimal/include/string.h
@@ -18,7 +18,9 @@ extern "C" {
 
 extern char  *strcpy(char *ZRESTRICT d, const char *ZRESTRICT s);
 extern char  *strerror(int errnum);
+#if _POSIX_C_SOURCE >= 200112L
 extern int   strerror_r(int errnum, char *strerrbuf, size_t buflen);
+#endif
 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/posix/CMakeLists.txt b/lib/posix/CMakeLists.txt
@@ -43,6 +43,7 @@ zephyr_library_sources_ifdef(CONFIG_POSIX_CLOCK clock.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_CLOCK nanosleep.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_CLOCK sleep.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_CLOCK timer.c)
+zephyr_library_sources_ifdef(CONFIG_POSIX_CX_STRERROR_R strerror_r.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_FS fs.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MQUEUE mqueue.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_SIGNAL signal.c ${STRSIGNAL_TABLE_H})

diff --git a/lib/posix/Kconfig b/lib/posix/Kconfig
@@ -54,3 +54,6 @@ source "lib/posix/Kconfig.signal"
 source "lib/posix/Kconfig.spinlock"
 source "lib/posix/Kconfig.timer"
 source "lib/posix/Kconfig.uname"
+
+# POSIX extensions to ISO C
+source "lib/posix/Kconfig.cx.string"
diff --git a/lib/posix/Kconfig.cx.string b/lib/posix/Kconfig.cx.string
@@ -0,0 +1,15 @@
+# Copyright (c) 2023 Meta
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# CX: Extension to the ISO C standard
+# See IEEE 1003.1-2017
+
+config POSIX_CX_STRERROR_R
+	bool "Get error message string"
+	default y if POSIX_API
+	select COMMON_LIBC_STRERROR
+	help
+	  Enable the strerror_r() POSIX C extension.
+
+	  This function is a thread-safe version of ISO C strerror().
diff --git a/lib/libc/minimal/source/string/strerror.c → lib/posix/strerror_r.c b/lib/libc/minimal/source/string/strerror.c → lib/posix/strerror_r.c
@@ -16,20 +16,7 @@
  * 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 (char *) "";
-}
+#include "libc/common/strerror_table.h"
 
 /*
  * See
@@ -41,7 +28,7 @@ int strerror_r(int errnum, char *strerrbuf, size_t buflen)
 	size_t msg_len;
 
 	if (errnum >= 0 && errnum < sys_nerr) {
-		if (IS_ENABLED(CONFIG_MINIMAL_LIBC_STRING_ERROR_TABLE)) {
+		if (IS_ENABLED(CONFIG_COMMON_LIBC_STRING_ERROR_TABLE)) {
 			msg = sys_errlist[errnum];
 			msg_len = sys_errlen[errnum];
 		} else {

diff --git a/scripts/build/gen_strerror_table.py b/scripts/build/gen_strerror_table.py
@@ -21,7 +21,25 @@ def front_matter(sys_nerr):
 
 #include <zephyr/sys/util.h>
 
-#define sys_nerr {sys_nerr}'''
+
+#define sys_nerr {sys_nerr}
+
+#ifndef __sys_errlist_declare
+
+extern const char *const sys_errlist[{sys_nerr}];
+extern const uint8_t sys_errlen[{sys_nerr}];
+
+#else
+
+const char *const sys_errlist[{sys_nerr}];
+const uint8_t sys_errlen[{sys_nerr}];
+'''
+
+def end_matter():
+    return f'''
+
+#endif /* __sys_errlist_declare */
+'''
 
 
 def gen_strerror_table(input, output):
@@ -61,7 +79,7 @@ def gen_strerror_table(input, output):
 
             # Generate string table
             print(
-                f'static const char *const sys_errlist[sys_nerr] = {{', file=outf)
+                f'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)
@@ -70,13 +88,15 @@ def gen_strerror_table(input, output):
 
             # Generate string lengths (includes trailing '\0')
             print(
-                f'static const uint8_t sys_errlen[sys_nerr] = {{', file=outf)
+                f'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)
 
+            print(end_matter(), file=outf)
+
 
 def parse_args():
     parser = argparse.ArgumentParser(allow_abbrev=False)