[PATCH v2 4/5] sim: Check known getopt definition existence

[Tsukasa OI <research_trasio@irq.a4lg.com>]

Clang generates a warning if there is a function declaration/definition
with zero arguments.  Such declarations/definitions without a prototype (an
argument list) are deprecated forms of indefinite arguments
("-Wdeprecated-non-prototype").  On the default configuration, it causes a
build failure (unless "--disable-werror" is specified).

include/getopt.h defines some getopt function definitions but one of them
has a form "extern int getopt ();".  If this form is selected in
include/getopt.h, Clang generates a warning and the build fails by default.

In really old environments, this getopt definition with no arguments is
necessary (because the definition may change between environments).
However, this definition is now a cause of problems on modern environments.

A good news is, this definition is not always selected (e.g. if used by
binutils/*.c).  This is because configuration scripts of binutils, gas,
gprof and ld tries to find known definition of getopt function is used and
defines HAVE_DECL_GETOPT macro.  If this macro is defined when getopt.h is
included, a good form of getopt is used and Clang won't generate warnings.

This commit adds a portion of ld/configure.ac to find the known getopt
definition.  If we could find one (and we *will* in most environments),
we don't need to rely on the deprecated definition.

sim/ChangeLog:

	* configure.ac: Find the known getopt definition in <unistd.h>.
	* configure: Regenerate.
	* config.h.in: Likewise.
---
 sim/config.h.in  |  3 +++
 sim/configure    | 32 ++++++++++++++++++++++++++++++++
 sim/configure.ac | 10 ++++++++++
 3 files changed, 45 insertions(+)

diff --git a/sim/config.h.in b/sim/config.h.in
index 8e84759df04..5091dc32a1b 100644
--- a/sim/config.h.in
+++ b/sim/config.h.in
@@ -41,6 +41,9 @@
 /* Define to 1 if you have the `chmod' function. */
 #undef HAVE_CHMOD
 
+/* Is the prototype for getopt in <unistd.h> in the expected format? */
+#undef HAVE_DECL_GETOPT
+
 /* Define to 1 if you have the declaration of `tzname', and to 0 if you don't.
    */
 #undef HAVE_DECL_TZNAME
diff --git a/sim/configure b/sim/configure
index b31c2f5d8f3..495f1b21ce9 100755
--- a/sim/configure
+++ b/sim/configure
@@ -16298,6 +16298,38 @@ $as_echo "${WARN_CFLAGS} ${WERROR_CFLAGS}" >&6; }
 fi
 
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for a known getopt prototype in unistd.h" >&5
+$as_echo_n "checking for a known getopt prototype in unistd.h... " >&6; }
+if ${ld_cv_decl_getopt_unistd_h+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <unistd.h>
+int
+main ()
+{
+extern int getopt (int, char *const*, const char *);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ld_cv_decl_getopt_unistd_h=yes
+else
+  ld_cv_decl_getopt_unistd_h=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ld_cv_decl_getopt_unistd_h" >&5
+$as_echo "$ld_cv_decl_getopt_unistd_h" >&6; }
+if test $ld_cv_decl_getopt_unistd_h = yes; then
+
+$as_echo "#define HAVE_DECL_GETOPT 1" >>confdefs.h
+
+fi
+
 
 
 
diff --git a/sim/configure.ac b/sim/configure.ac
index 66a1020efe0..c24c676d4da 100644
--- a/sim/configure.ac
+++ b/sim/configure.ac
@@ -177,6 +177,16 @@ SIM_AC_OPTION_STDIO
 SIM_AC_OPTION_TRACE
 SIM_AC_OPTION_WARNINGS
 
+AC_MSG_CHECKING(for a known getopt prototype in unistd.h)
+AC_CACHE_VAL(ld_cv_decl_getopt_unistd_h,
+[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <unistd.h>], [extern int getopt (int, char *const*, const char *);])],
+ld_cv_decl_getopt_unistd_h=yes, ld_cv_decl_getopt_unistd_h=no)])
+AC_MSG_RESULT($ld_cv_decl_getopt_unistd_h)
+if test $ld_cv_decl_getopt_unistd_h = yes; then
+  AC_DEFINE([HAVE_DECL_GETOPT], 1,
+	    [Is the prototype for getopt in <unistd.h> in the expected format?])
+fi
+
 dnl These are unfortunate.  They are conditionally called by other sim macros
 dnl but always used by common/Make-common.in.  So we have to subst here even
 dnl when the rest of the code is in the respective macros.  Once we merge the
-- 
2.34.1