games-emulation/dolphin: Backport gcc-14 build fix

Thanks to Kostadin Shishmanov for finding the pull request.

Closes: https://bugs.gentoo.org/933203
Signed-off-by: Michał Górny <mgorny@gentoo.org>

games-emulation/dolphin/dolphin-5.0_p20220520-r2.ebuild

@@ -35,7 +35,11 @@ IUSE="
 	profile pulseaudio systemd upnp vulkan
 "
 
-PATCHES=("${FILESDIR}/${P}-libfmt-9.0.0-fix-build.patch")
+PATCHES=(
+	"${FILESDIR}/${P}-libfmt-9.0.0-fix-build.patch"
+	# https://github.com/dolphin-emu/dolphin/pull/12575
+	"${FILESDIR}/${P}-gcc-14.patch"
+)
 
 RDEPEND="
 	app-arch/bzip2:=

games-emulation/dolphin/files/dolphin-5.0_p20220520-gcc-14.patch

@@ -0,0 +1,30 @@
+From 3da2e15e6b95f02f66df461e87c8b896e450fdab Mon Sep 17 00:00:00 2001
+From: Peter Lafreniere <peter@n8pjl.ca>
+Date: Sun, 11 Feb 2024 20:55:31 -0500
+Subject: [PATCH] IOFile: avoid clearing errors on null file struct
+
+When performing a default compilation with recent GCC & glibc,
+the use of -Werror=nonnull causes a build error.
+
+The error is given as IOFile::ClearError() can call std::clearerr()
+with a null file, which can trigger a null-pointer dereference in libc.
+
+Change the std::clearerr() call to be conditional on a file being open.
+---
+ Source/Core/Common/IOFile.h | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/Source/Core/Common/IOFile.h b/Source/Core/Common/IOFile.h
+index 4b12c3188853..b5895333b1be 100644
+--- a/Source/Core/Common/IOFile.h
++++ b/Source/Core/Common/IOFile.h
+@@ -116,7 +116,8 @@ class IOFile
+   void ClearError()
+   {
+     m_good = true;
+-    std::clearerr(m_file);
++    if (IsOpen())
++      std::clearerr(m_file);
+   }
+ 
+ private: