Set the proper type for variables set in signal handlers

* bootstrap.conf: Get gnulib's sig_atomic_t type checking M4 macro.
* configure.ac: Invoke it.
* src/makeint.h (handling_fatal_signal): Set the type correctly.
* src/commands.c (handling_fatal_signal): Ditto.

bootstrap.conf

@@ -47,7 +47,7 @@ automake   1.16.1
 "
 
 gnulib_name=libgnu
-gnulib_files=doc/make-stds.texi
+gnulib_files="doc/make-stds.texi m4/sig_atomic_t.m4"
 
 # Using the full strtoll module pulls in a lot of stuff.  But, it's pretty
 # simple to use just the base source file, so pull that.  We'll use it in

configure.ac

@@ -78,6 +78,9 @@ AC_TYPE_SSIZE_T
 AC_TYPE_INTMAX_T
 AC_TYPE_UINTMAX_T
 
+# Check for sig_atomic_t
+gt_TYPE_SIG_ATOMIC_T
+
 # Find out whether our struct stat returns nanosecond resolution timestamps.
 
 AC_STRUCT_ST_MTIM_NSEC

src/commands.c

@@ -479,7 +479,7 @@ execute_file_commands (struct file *file)
 /* This is set while we are inside fatal_error_signal,
    so things can avoid nonreentrant operations.  */
 
-int handling_fatal_signal = 0;
+volatile sig_atomic_t handling_fatal_signal = 0;
 
 /* Handle fatal signals.  */
 

src/makeint.h

@@ -791,7 +791,7 @@ extern char *version_string, *remote_description, *make_host;
 
 extern unsigned int commands_started;
 
-extern int handling_fatal_signal;
+extern volatile sig_atomic_t handling_fatal_signal;
 
 #ifndef MIN
 #define MIN(_a,_b) ((_a)<(_b)?(_a):(_b))