Fix configure check for symbol versioning with GCC 10 (rhbz #1862745)

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

0001-configure-fix-symver-support-checks.patch

@@ -0,0 +1,66 @@
+From be61c7fd7d60f57dcc07e6a7c5d3d49938546b61 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Ferenc=20W=C3=A1gner?= <wferi@debian.org>
+Date: Sat, 18 Jul 2020 12:35:30 +0200
+Subject: [PATCH] configure: fix symver support checks
+
+The versioned test symbols must be external, so move them into the
+prologue, otherwise GCC 9.3 (at least) reports "Error: invalid attempt
+to declare external version name as default in symbol `f@@VER2'".
+Also suppress warnings about missing prototypes and return
+statements for these test functions.
+---
+ configure.ac                 | 11 ++++++-----
+ libgphoto2_port/configure.ac | 11 ++++++-----
+ 2 files changed, 12 insertions(+), 10 deletions(-)
+
+diff --git a/configure.ac b/configure.ac
+index f73c81d88..51d1e18b3 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -259,13 +259,14 @@ AC_SYS_LARGEFILE
+ 
+ AC_MSG_CHECKING([for asm .symver support])
+ AC_COMPILE_IFELSE([dnl
+-	AC_LANG_PROGRAM([[]],[[
+-		int f1() { }
+-		int f2() { }
++	AC_LANG_PROGRAM([[
++		void f1(void);
++		void f1() {}
++		void f2(void);
++		void f2() {}
+ 		asm(".symver f1, f@VER1");
+ 		asm(".symver f2, f@@VER2");
+-		int main(int argc, char **argv) { }
+-	]])dnl
++	]],[])dnl
+ ],[
+ 	AC_DEFINE([HAVE_ASM_SYMVERS],1,[Define if there is asm .symver support.])
+ 	VERSIONMAPLDFLAGS="-Wl,--version-script=\$(srcdir)/libgphoto2.ver"
+diff --git a/libgphoto2_port/configure.ac b/libgphoto2_port/configure.ac
+index 6af8bd914..a8546aa36 100644
+--- a/libgphoto2_port/configure.ac
++++ b/libgphoto2_port/configure.ac
+@@ -165,13 +165,14 @@ AC_CHECK_LIB([regex],[regexec])
+ 
+ AC_MSG_CHECKING([for asm .symver support])
+ AC_COMPILE_IFELSE([dnl
+-	AC_LANG_PROGRAM([[]],[[
+-		int f1() { }
+-		int f2() { }
++	AC_LANG_PROGRAM([[
++		void f1(void);
++		void f1() {}
++		void f2(void);
++		void f2() {}
+ 		asm(".symver f1, f@VER1");
+ 		asm(".symver f2, f@@VER2");
+-		int main(int argc, char **argv) { }
+-	]])dnl
++	]],[])dnl
+ ],[
+ 	AC_DEFINE([HAVE_ASM_SYMVERS],1,[Define if there is asm .symver support.])
+ 	VERSIONMAPLDFLAGS="-Wl,--version-script=\$(srcdir)/libgphoto2_port.ver"
+-- 
+2.26.2
+

libgphoto2.spec

@@ -5,7 +5,7 @@
 
 Name:           libgphoto2
 Version:        2.5.24
-Release:        3%{?dist}
+Release:        4%{?dist}
 Summary:        Library for accessing digital cameras
 # GPLV2+ for the main lib (due to exif.c) and most plugins, some plugins GPLv2
 License:        GPLv2+ and GPLv2
@@ -14,6 +14,7 @@ URL:            http://www.gphoto.org/
 Source0:        http://downloads.sourceforge.net/gphoto/%{name}-%{version}.tar.bz2
 Patch1:         gphoto2-pkgcfg.patch
 Patch2:         gphoto2-device-return.patch
+Patch3:         0001-configure-fix-symver-support-checks.patch
 
 BuildRequires:  gcc
 BuildRequires:  gcc-c++
@@ -37,6 +38,9 @@ BuildRequires:  pkgconfig(libusb-1.0)
 Requires:       lockdev
 # -----------------------------------
 
+# Temporarily required for patch3
+BuildRequires: autoconf automake libtool gettext-devel
+
 %description
 libgphoto2 is a library that can be used by applications to access
 various digital cameras. libgphoto2 itself is not a GUI application,
@@ -65,6 +69,9 @@ for f in AUTHORS ChangeLog COPYING libgphoto2_port/AUTHORS libgphoto2_port/COPYI
 done
 
 %build
+# Temporarily required for patch3
+autoreconf -if
+
 %configure \
     udevscriptdir='%{udevdir}'   \
     --with-drivers=all           \
@@ -145,6 +152,9 @@ rm -rf %{buildroot}%{_datadir}/libgphoto2_port/*/vcamera/
 %{_mandir}/man3/%{name}_port.3*
 
 %changelog
+* Thu Aug  6 2020 Daniel P. Berrangé <berrange@redhat.com> - 2.5.24-4
+- Fix configure check for symbol versioning with GCC 10 (rhbz #1862745)
+
 * Tue Jul 28 2020 Fedora Release Engineering <releng@fedoraproject.org> - 2.5.24-3
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_33_Mass_Rebuild