From 1b99854649bb8641770cf89ea361a2674256e223 Mon Sep 17 00:00:00 2001
From: Christoph Reiter <reiter.christoph@gmail.com>
Date: Mon, 24 Mar 2025 20:40:04 +0100
Subject: [PATCH] Fix extern C wrapping glib headers

extern C was wrapping the includes of headers which in turn included
glib.h. glib 2.84 started to include C++ code in some of its headers
which breaks when wrapped with extern C, see
https://gitlab.gnome.org/GNOME/glib/-/issues/3631

Fix by only wrapping our own code with extern C.

Fixes https://gitlab.com/inkscape/inkscape/-/issues/5615
---
 src/path/splinefit/bezier-fit.cpp | 6 ++----
 src/path/splinefit/splinefit.h    | 5 +++++
 src/path/splinefit/splinefont.h   | 4 ++++
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/path/splinefit/bezier-fit.cpp b/src/path/splinefit/bezier-fit.cpp
index 111f538590..ed506da79d 100644
--- a/src/path/splinefit/bezier-fit.cpp
+++ b/src/path/splinefit/bezier-fit.cpp
@@ -6,10 +6,8 @@
 #include <2geom/bezier-utils.h>
 #include <2geom/point.h>
 
-extern "C" {
-    #include "splinefit.h"
-    #include "splinefont.h"
-}
+#include "splinefit.h"
+#include "splinefont.h"
 
 int bezier_fit(Geom::Point bezier[4], const std::vector<InputPoint>& data) {
 
diff --git a/src/path/splinefit/splinefit.h b/src/path/splinefit/splinefit.h
index 22e21fcdbe..89f830e548 100644
--- a/src/path/splinefit/splinefit.h
+++ b/src/path/splinefit/splinefit.h
@@ -32,6 +32,8 @@
 // #include <fontforge-config.h>
 #include "splinefont.h"
 
+G_BEGIN_DECLS
+
 typedef struct fitpoint {
     BasePoint p;
     BasePoint ut;
@@ -75,4 +77,7 @@ extern SplinePoint *ApproximateSplineSetFromGen(SplinePoint *from, SplinePoint *
                                                 bigreal toler, int toler_is_sumsq,
                                                 GenPointsP genp, void *tok, int order2);
 
+
+G_END_DECLS
+
 #endif /* FONTFORGE_SPLINEFIT_H */
diff --git a/src/path/splinefit/splinefont.h b/src/path/splinefit/splinefont.h
index 83db934cec..f8aaaa82b7 100644
--- a/src/path/splinefit/splinefont.h
+++ b/src/path/splinefit/splinefont.h
@@ -5,6 +5,8 @@
 
 #include <glib.h>
 
+G_BEGIN_DECLS
+
 typedef double real;
 typedef double bigreal;
 typedef double extended;
@@ -188,4 +190,6 @@ enum pconvert_flags {
 
 void SplinesRemoveBetween(SplinePoint *from, SplinePoint *to, int type);
 
+G_END_DECLS
+
 #endif // _SEEN_SPLINEFONT_H_
-- 
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