posix: unistd: support for confstr()

doc/services/portability/posix/aep/index.rst

@@ -30,7 +30,7 @@ Minimal Realtime System Profile (PSE51)
     POSIX_DEVICE_IO,, :ref:`†<posix_undefined_behaviour>`
     POSIX_FILE_LOCKING,,
     POSIX_SIGNALS,, :ref:`†<posix_undefined_behaviour>`
-    POSIX_SINGLE_PROCESS,, :ref:`†<posix_undefined_behaviour>`
+    POSIX_SINGLE_PROCESS, yes,
     POSIX_THREADS_BASE, yes, :ref:`†<posix_undefined_behaviour>`
     XSI_THREADS_EXT, yes, :ref:`†<posix_undefined_behaviour>`
 
@@ -82,7 +82,7 @@ Realtime Controller System Profile (PSE52)
     POSIX_FILE_LOCKING,,
     POSIX_FILE_SYSTEM,,
     POSIX_SIGNALS,, :ref:`†<posix_undefined_behaviour>`
-    POSIX_SINGLE_PROCESS,, :ref:`†<posix_undefined_behaviour>`
+    POSIX_SINGLE_PROCESS, yes,
     POSIX_THREADS_BASE, yes, :ref:`†<posix_undefined_behaviour>`
     XSI_THREADS_EXT, yes, :ref:`†<posix_undefined_behaviour>`
 
@@ -143,7 +143,7 @@ Dedicated Realtime System Profile (PSE53)
     POSIX_PIPE,, :ref:`†<posix_undefined_behaviour>`
     POSIX_SIGNALS,, :ref:`†<posix_undefined_behaviour>`
     POSIX_SIGNAL_JUMP,, :ref:`†<posix_undefined_behaviour>`
-    POSIX_SINGLE_PROCESS,, :ref:`†<posix_undefined_behaviour>`
+    POSIX_SINGLE_PROCESS, yes,
     POSIX_THREADS_BASE, yes, :ref:`†<posix_undefined_behaviour>`
     XSI_THREADS_EXT, yes, :ref:`†<posix_undefined_behaviour>`
 

doc/services/portability/posix/option_groups/index.rst

@@ -163,7 +163,7 @@ process applications.
    :header: API, Supported
    :widths: 50,10
 
-    confstr(),
+    confstr(),yes
     environ,yes
     errno,yes
     getenv(),yes

include/zephyr/posix/sys/confstr.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2024, Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#ifndef ZEPHYR_INCLUDE_POSIX_SYS_CONFSTR_H_
+#define ZEPHYR_INCLUDE_POSIX_SYS_CONFSTR_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum {
+	_CS_PATH,
+	_CS_POSIX_V7_ILP32_OFF32_CFLAGS,
+	_CS_POSIX_V7_ILP32_OFF32_LDFLAGS,
+	_CS_POSIX_V7_ILP32_OFF32_LIBS,
+	_CS_POSIX_V7_ILP32_OFFBIG_CFLAGS,
+	_CS_POSIX_V7_ILP32_OFFBIG_LDFLAGS,
+	_CS_POSIX_V7_ILP32_OFFBIG_LIBS,
+	_CS_POSIX_V7_LP64_OFF64_CFLAGS,
+	_CS_POSIX_V7_LP64_OFF64_LDFLAGS,
+	_CS_POSIX_V7_LP64_OFF64_LIBS,
+	_CS_POSIX_V7_LPBIG_OFFBIG_CFLAGS,
+	_CS_POSIX_V7_LPBIG_OFFBIG_LDFLAGS,
+	_CS_POSIX_V7_LPBIG_OFFBIG_LIBS,
+	_CS_POSIX_V7_THREADS_CFLAGS,
+	_CS_POSIX_V7_THREADS_LDFLAGS,
+	_CS_POSIX_V7_WIDTH_RESTRICTED_ENVS,
+	_CS_V7_ENV,
+	_CS_POSIX_V6_ILP32_OFF32_CFLAGS,
+	_CS_POSIX_V6_ILP32_OFF32_LDFLAGS,
+	_CS_POSIX_V6_ILP32_OFF32_LIBS,
+	_CS_POSIX_V6_ILP32_OFFBIG_CFLAGS,
+	_CS_POSIX_V6_ILP32_OFFBIG_LDFLAGS,
+	_CS_POSIX_V6_ILP32_OFFBIG_LIBS,
+	_CS_POSIX_V6_LP64_OFF64_CFLAGS,
+	_CS_POSIX_V6_LP64_OFF64_LDFLAGS,
+	_CS_POSIX_V6_LP64_OFF64_LIBS,
+	_CS_POSIX_V6_LPBIG_OFFBIG_CFLAGS,
+	_CS_POSIX_V6_LPBIG_OFFBIG_LDFLAGS,
+	_CS_POSIX_V6_LPBIG_OFFBIG_LIBS,
+	_CS_POSIX_V6_WIDTH_RESTRICTED_ENVS,
+	_CS_V6_ENV,
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_INCLUDE_POSIX_SYS_CONFSTR_H_ */

include/zephyr/posix/unistd.h

@@ -19,6 +19,7 @@
 #ifdef CONFIG_POSIX_SYSCONF
 #include <zephyr/posix/signal.h>
 #endif
+#include <zephyr/posix/sys/confstr.h>
 #include <zephyr/posix/sys/stat.h>
 #include <zephyr/posix/sys/sysconf.h>
 
@@ -266,6 +267,9 @@ int usleep(useconds_t useconds);
 #ifdef CONFIG_POSIX_SYSCONF_IMPL_FULL
 long sysconf(int opt);
 #endif
+#if _POSIX_C_SOURCE >= 2
+size_t confstr(int name, char *buf, size_t len);
+#endif
 
 #ifdef __cplusplus
 }

lib/posix/options/CMakeLists.txt

@@ -40,6 +40,7 @@ zephyr_library_sources_ifdef(CONFIG_POSIX_API perror.c)
 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_CONFSTR confstr.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_ENV env.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_FS fs.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MQUEUE mqueue.c)

lib/posix/options/Kconfig

@@ -27,6 +27,7 @@ endif # POSIX_CLOCK
 rsource "Kconfig.barrier"
 rsource "Kconfig.clock"
 rsource "Kconfig.cond"
+rsource "Kconfig.confstr"
 rsource "Kconfig.env"
 rsource "Kconfig.eventfd"
 rsource "Kconfig.fdtable"

lib/posix/options/Kconfig.confstr

@@ -0,0 +1,9 @@
+# Copyright (c) 2024, Meta
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config POSIX_CONFSTR
+	bool "Retrieve string system configuration"
+	default y if POSIX_API
+	help
+	  This enables the POSIX confstr() function.

lib/posix/options/confstr.c

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2024, Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/posix/unistd.h>
+
+size_t confstr(int name, char *buf, size_t len)
+{
+	if (name < 0 || name > _CS_V6_ENV) {
+		errno = EINVAL;
+		return 0;
+	}
+
+	if (buf != NULL && len > 0) {
+		buf[0] = '\0';
+	}
+
+	return 1;
+}

tests/posix/common/CMakeLists.txt

@@ -8,3 +8,5 @@ FILE(GLOB app_sources src/*.c)
 zephyr_include_directories(${ZEPHYR_BASE}/lib/posix)
 
 target_sources(app PRIVATE ${app_sources})
+
+target_compile_options(app PRIVATE -U_POSIX_C_SOURCE -D_POSIX_C_SOURCE=200809L)

tests/posix/common/src/confstr.c

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2024, Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <errno.h>
+#include <unistd.h>
+
+#include <zephyr/ztest.h>
+#include <zephyr/sys/util.h>
+
+ZTEST(confstr, test_confstr)
+{
+	char buf[1];
+
+	/* degenerate cases */
+	{
+		struct arg {
+			int name;
+			char *buf;
+			size_t len;
+		};
+
+		const struct arg arg1s[] = {
+			{-1, NULL, 0},
+			{-1, NULL, sizeof(buf)},
+			{-1, buf, 0},
+			{-1, buf, sizeof(buf)},
+		};
+
+		const struct arg arg2s[] = {
+			{_CS_PATH, NULL, 0},
+			{_CS_PATH, buf, 0},
+		};
+
+		const struct arg arg3s[] = {
+			{_CS_PATH, NULL, sizeof(buf)},
+		};
+
+		ARRAY_FOR_EACH_PTR(arg1s, arg) {
+			errno = 0;
+			zassert_equal(0, confstr(arg->name, arg->buf, arg->len));
+			zassert_equal(errno, EINVAL);
+		}
+
+		ARRAY_FOR_EACH_PTR(arg2s, arg) {
+			errno = 0;
+			buf[0] = 0xff;
+			zassert_true(confstr(arg->name, arg->buf, arg->len) > 0);
+			zassert_equal(errno, 0);
+			zassert_equal((uint8_t)buf[0], 0xff);
+		}
+
+		ARRAY_FOR_EACH_PTR(arg3s, arg) {
+			errno = 0;
+			zassert_true(confstr(arg->name, arg->buf, arg->len) > 0);
+			zassert_equal(errno, 0);
+		}
+	}
+
+	buf[0] = 0xff;
+	zassert_true(confstr(_CS_PATH, buf, sizeof(buf) > 0));
+	zassert_equal(buf[0], '\0');
+}
+
+ZTEST_SUITE(confstr, NULL, NULL, NULL, NULL, NULL);