[PATCH 15/16] gdb: remove redundant snprintf declaration check

[Simon Marchi <simon.marchi@efficios.com>]

configure.ac checks for the snprintf declaration, but libiberty_INIT
already does it.  Remove the check from configure.ac.

The only user of HAVE_DECL_SNPRINTF in GDB is a check in
python-internal.h, which defines HAVE_SNPRINTF on Windows, to prevent
older Python headers from redefining snprintf to _snprintf.  It uses
"defined (HAVE_DECL_SNPRINTF)", which is always true, since
AC_CHECK_DECLS defines HAVE_DECL_SNPRINTF to either 0 or 1.  Since it
apparently worked fine like this for a while, simplify the condition to
just check _WIN32.  snprintf is standard in C++11 anyway.

I checked whether defining HAVE_SNPRINTF is still needed at all.  It is
no longer necessary since CPython commit e822e37946f2 ("bpo-36020:
Remove snprintf macro in pyerrors.h (GH-20889)", 2020-06-15), which is
available since Python 3.9.  So once we drop support for Python 3.8 and
below, this can go.  Add a note in the source about that.

Regenerate configure.

Change-Id: I431ccdf7d67a673c8a01ba4f34378a040a4c7bc6
---
 gdb/configure                | 11 -----------
 gdb/configure.ac             |  1 -
 gdb/python/python-internal.h |  7 +++++--
 3 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/gdb/configure b/gdb/configure
index 5290d29efbce..cfe994c3842a 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -29426,17 +29426,6 @@ _ACEOF
 
 
 
-ac_fn_c_check_decl "$LINENO" "snprintf" "ac_cv_have_decl_snprintf" "$ac_includes_default"
-if test "x$ac_cv_have_decl_snprintf" = xyes; then :
-  ac_have_decl=1
-else
-  ac_have_decl=0
-fi
-
-cat >>confdefs.h <<_ACEOF
-#define HAVE_DECL_SNPRINTF $ac_have_decl
-_ACEOF
-
 
   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for LC_MESSAGES" >&5
 $as_echo_n "checking for LC_MESSAGES... " >&6; }
diff --git a/gdb/configure.ac b/gdb/configure.ac
index b1e0a82b9b07..d10b20f5a17d 100644
--- a/gdb/configure.ac
+++ b/gdb/configure.ac
@@ -1488,7 +1488,6 @@ AC_CHECK_HEADERS([execinfo.h])
 
 libiberty_INIT
 
-AC_CHECK_DECLS([snprintf])
 AM_LC_MESSAGES
 
 # ------------------ #
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index 5f023b0d9719..5af06d02a51a 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -39,8 +39,11 @@
    around technique as above.  */
 #undef _FILE_OFFSET_BITS
 
-/* A kludge to avoid redefinition of snprintf on Windows by pyerrors.h.  */
-#if defined(_WIN32) && defined(HAVE_DECL_SNPRINTF)
+/* A kludge to avoid redefinition of snprintf on Windows by pyerrors.h.
+
+   This is only needed for Python <= 3.8, so it can go once support for those
+   Python versions is dropped.  */
+#ifdef _WIN32
 #define HAVE_SNPRINTF 1
 #endif
 
-- 
2.56.0