analyzer: Add exit, and _exit replacement, to sm-signal.

Warn about using exit in signal handler and suggest _exit as alternative.

gcc/analyzer/ChangeLog:

	* sm-signal.cc(signal_unsafe_call::emit): Possibly add
	gcc_rich_location note for replacement.
	(signal_unsafe_call::get_replacement_fn): New private function.
	(get_async_signal_unsafe_fns): Add "exit".

gcc/testsuite/ChangeLog:

	* gcc.dg/analyzer/signal-exit.c: New testcase.

1 files changed, 23 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/analyzer/signal-exit.c b/gcc/testsuite/gcc.dg/analyzer/signal-exit.c
new file mode 100644
index 0000000..a567124
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/signal-exit.c
@@ -0,0 +1,23 @@
+/* Example of a bad call within a signal handler with replacement
+   alternative.  'handler' calls 'exit', and 'exit' is not allowed
+   from a signal handler.  But '_exit' is allowed.  */
+
+#include <signal.h>
+#include <stdlib.h>
+
+extern void body_of_program(void);
+
+static void handler(int signum)
+{
+  exit(1); /* { dg-warning "call to 'exit' from within signal handler" "warning" } */
+  /* { dg-message "note: '_exit' is a possible signal-safe alternative for 'exit'" "replacement note" { target *-*-* } .-1 } */
+}
+
+int main(int argc, const char *argv)
+{
+  signal(SIGINT, handler); /* { dg-message "registering 'handler' as signal handler" } */
+
+  body_of_program();
+
+  return 0;
+}