posix: signal: include_next to get the libc signal() decl

include/zephyr/posix/posix_types.h

@@ -35,7 +35,6 @@ typedef uint32_t clockid_t;
 typedef unsigned long timer_t;
 #endif
 
-#ifdef CONFIG_PTHREAD_IPC
 /* Thread attributes */
 struct pthread_attr {
  int priority;
@@ -101,8 +100,6 @@ typedef struct pthread_rwlock_obj {
  k_tid_t wr_owner;
 } pthread_rwlock_t;
 
-#endif /* CONFIG_PTHREAD_IPC */
-
 #ifdef __cplusplus
 }
 #endif

include/zephyr/posix/signal.h

@@ -8,11 +8,10 @@
 
 #include "posix_types.h"
 
-#ifdef __cplusplus
-extern "C" {
-#endif
+#define SIG_DFL ((sighandler_t)0)
+#define SIG_ERR ((sighandler_t)1)
+#define SIG_IGN ((sighandler_t)-1)
 
-#ifdef CONFIG_POSIX_SIGNAL
 #define SIGHUP 1 /**< Hangup */
 #define SIGINT 2 /**< Interrupt */
 #define SIGQUIT 3 /**< Quit */
@@ -51,6 +50,10 @@ extern "C" {
 
 BUILD_ASSERT(CONFIG_POSIX_RTSIG_MAX >= 0);
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 typedef struct {
  unsigned long sig[DIV_ROUND_UP(_NSIG, BITS_PER_LONG)];
 } sigset_t;
@@ -61,7 +64,6 @@ int sigfillset(sigset_t *set);
 int sigaddset(sigset_t *set, int signo);
 int sigdelset(sigset_t *set, int signo);
 int sigismember(const sigset_t *set, int signo);
-#endif /* CONFIG_POSIX_SIGNAL */
 
 #ifndef SIGEV_NONE
 #define SIGEV_NONE 1
@@ -92,6 +94,9 @@ typedef struct sigevent {
  #endif
 } sigevent;
 
+typedef void (*sighandler_t)(int signo);
+sighandler_t signal(int signum, sighandler_t handler);
+
 #ifdef __cplusplus
 }
 #endif

lib/libc/minimal/CMakeLists.txt

@@ -10,6 +10,7 @@ set(STRERROR_TABLE_H ${GEN_DIR}/libc/minimal/strerror_table.h)
 zephyr_library_cc_option(-fno-builtin)
 
 zephyr_library_sources(
+ source/signal/signal.c
  source/stdlib/atoi.c
  source/stdlib/strtol.c
  source/stdlib/strtoul.c

lib/libc/minimal/include/signal.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2023 Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_SIGNAL_H_
+#define ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_SIGNAL_H_
+
+#define SIG_DFL ((sighandler_t)0)
+#define SIG_ERR ((sighandler_t)1)
+#define SIG_IGN ((sighandler_t)-1)
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef int sig_atomic_t; /* Atomic entity type (ANSI) */
+
+/* Note: sighandler_t is a gnu-ism, but it simplifies the declaration below */
+typedef void (*sighandler_t)(int signo);
+
+sighandler_t signal(int signum, sighandler_t handler);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_SIGNAL_H_ */

lib/libc/minimal/source/signal/signal.c

@@ -0,0 +1,12 @@
+/*
+ * Copyright (c) 2023 Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <signal.h>
+
+sighandler_t signal(int signum, sighandler_t handler)
+{
+ return SIG_DFL;
+}

lib/posix/Kconfig.signal

@@ -8,14 +8,15 @@ config POSIX_SIGNAL
  help
  Enable support for POSIX signal APIs.
 
-if POSIX_SIGNAL
 config POSIX_RTSIG_MAX
  int "Maximum number of realtime signals"
  default 31
  help
  Define the maximum number of realtime signals (RTSIG_MAX).
  The range of realtime signals is [SIGRTMIN .. (SIGRTMIN+RTSIG_MAX)]
 
+if POSIX_SIGNAL
+
 config POSIX_SIGNAL_STRING_DESC
  bool "Use full description for the strsignal API"
  default y

lib/posix/Kconfig.timer

@@ -7,6 +7,10 @@ type = timer_t
 type-function = timer_create
 source "lib/posix/Kconfig.template.pooled_type"
 
+config POSIX_TIMER
+ bool
+ imply POSIX_SIGNAL
+
 config TIMER_CREATE_WAIT
  int "Time to wait for timer availability (in msec) in POSIX application"
  default 100

lib/posix/signal.c

@@ -10,6 +10,8 @@
 
 #include <zephyr/posix/signal.h>
 
+BUILD_ASSERT(CONFIG_POSIX_RTSIG_MAX >= 0);
+
 #define SIGNO_WORD_IDX(_signo) (signo / BITS_PER_LONG)
 #define SIGNO_WORD_BIT(_signo) (signo & BIT_MASK(LOG2(BITS_PER_LONG)))
 

tests/lib/c_lib/src/test_signal_decl.c

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2023 Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <signal.h>
+
+#include <zephyr/ztest.h>
+
+ZTEST(test_c_lib, test_signal_decl)
+{
+ /*
+ * Even though the use of the ANSI-C function "signal()" is not yet
+ * supported in Zephyr, some users depend on it being declared (i.e.
+ * without CONFIG_POSIX_API=y and with with CONFIG_POSIX_SIGNAL=n).
+ */
+
+ zassert_not_null(signal);
+}

tests/posix/headers/prj.conf

@@ -18,3 +18,4 @@ CONFIG_POSIX_CLOCK=y
 CONFIG_POSIX_MQUEUE=y
 CONFIG_EVENTFD=y
 CONFIG_GETOPT=y
+CONFIG_POSIX_SIGNAL=y

tests/posix/headers/src/signal_h.c

@@ -19,12 +19,17 @@
  */
 ZTEST(posix_headers, test_signal_h)
 {
+ /* part of ANSI C */
+ zassert_not_null(signal);
+ /* part of ISO C */
+ zassert_not_equal(sizeof(sig_atomic_t), 0);
+
+#ifdef CONFIG_POSIX_API
  /* zassert_not_equal(-1, SIG_DFL); */ /* not implemented */
  /* zassert_not_equal(-1, SIG_ERR); */ /* not implemented */
  /* zassert_not_equal(-1, SIG_HOLD); */ /* not implemented */
  /* zassert_not_equal(-1, SIG_IGN); */ /* not implemented */
 
- /* zassert_not_equal((sig_atomic_t)-1, (sig_atomic_t)0); */ /* not implemented */
  /* zassert_not_equal((pid_t)-1, (pid_t)0); */ /* not implemented */
 
  zassert_not_equal(-1, offsetof(struct sigevent, sigev_notify));
@@ -130,7 +135,6 @@ ZTEST(posix_headers, test_signal_h)
  /* zassert_not_equal(-1, SI_ASYNCIO); */ /* not implemented */
  /* zassert_not_equal(-1, SI_MESGQ); */ /* not implemented */
 
-#ifdef CONFIG_POSIX_SIGNAL
  zassert_true(SIGRTMIN >= 0);
  zassert_true(SIGRTMAX >= SIGRTMIN);
  zassert_not_equal(-1, SIGABRT);
@@ -157,38 +161,34 @@ ZTEST(posix_headers, test_signal_h)
  zassert_not_equal(-1, SIGURG);
  zassert_not_equal(-1, SIGXCPU);
  zassert_not_equal(-1, SIGXFSZ);
- zassert_not_equal(((sigset_t){.sig[0] = 0}).sig[0], ((sigset_t){.sig[0] = -1}).sig[0]);
+ zassert_not_equal(sizeof(sigset_t), 0);
  zassert_not_null(sigemptyset);
  zassert_not_null(sigfillset);
  zassert_not_null(sigaddset);
  zassert_not_null(sigdelset);
  zassert_not_null(sigismember);
  zassert_not_null(strsignal);
-#endif /* CONFIG_POSIX_SIGNAL */
-
- if (IS_ENABLED(CONFIG_POSIX_API)) {
- /* zassert_not_null(kill); */ /* not implemented */
- /* zassert_not_null(killpg); */ /* not implemented */
- /* zassert_not_null(psiginfo); */ /* not implemented */
- /* zassert_not_null(psignal); */ /* not implemented */
- /* zassert_not_null(pthread_kill); */ /* not implemented */
- /* zassert_not_null(pthread_sigmask); */ /* not implemented */
- /* zassert_not_null(raise); */ /* not implemented */
- /* zassert_not_null(sigaction); */ /* not implemented */
- /* zassert_not_null(sigaltstack); */ /* not implemented */
- /* zassert_not_null(sighold); */ /* not implemented */
- /* zassert_not_null(sigignore); */ /* not implemented */
- /* zassert_not_null(siginterrupt); */ /* not implemented */
- /* zassert_not_null(signal); */ /* not implemented */
- /* zassert_not_null(sigpause); */ /* not implemented */
- /* zassert_not_null(sigpending); */ /* not implemented */
- /* zassert_not_null(sigprocmask); */ /* not implemented */
- /* zassert_not_null(sigqueue); */ /* not implemented */
- /* zassert_not_null(sigrelse); */ /* not implemented */
- /* zassert_not_null(sigset); */ /* not implemented */
- /* zassert_not_null(sigsuspend); */ /* not implemented */
- /* zassert_not_null(sigtimedwait); */ /* not implemented */
- /* zassert_not_null(sigwait); */ /* not implemented */
- /* zassert_not_null(sigwaitinfo); */ /* not implemented */
- }
+ /* zassert_not_null(kill); */ /* not implemented */
+ /* zassert_not_null(killpg); */ /* not implemented */
+ /* zassert_not_null(psiginfo); */ /* not implemented */
+ /* zassert_not_null(psignal); */ /* not implemented */
+ /* zassert_not_null(pthread_kill); */ /* not implemented */
+ /* zassert_not_null(pthread_sigmask); */ /* not implemented */
+ /* zassert_not_null(raise); */ /* not implemented */
+ /* zassert_not_null(sigaction); */ /* not implemented */
+ /* zassert_not_null(sigaltstack); */ /* not implemented */
+ /* zassert_not_null(sighold); */ /* not implemented */
+ /* zassert_not_null(sigignore); */ /* not implemented */
+ /* zassert_not_null(siginterrupt); */ /* not implemented */
+ /* zassert_not_null(sigpause); */ /* not implemented */
+ /* zassert_not_null(sigpending); */ /* not implemented */
+ /* zassert_not_null(sigprocmask); */ /* not implemented */
+ /* zassert_not_null(sigqueue); */ /* not implemented */
+ /* zassert_not_null(sigrelse); */ /* not implemented */
+ /* zassert_not_null(sigset); */ /* not implemented */
+ /* zassert_not_null(sigsuspend); */ /* not implemented */
+ /* zassert_not_null(sigtimedwait); */ /* not implemented */
+ /* zassert_not_null(sigwait); */ /* not implemented */
+ /* zassert_not_null(sigwaitinfo); */ /* not implemented */
+#endif
 }