From e432e78d1cbe08a00ff1c2ea4dc05cedcc842627 Mon Sep 17 00:00:00 2001
From: Pierre Bourdon <delroth@gmail.com>
Date: Sat, 17 Apr 2021 14:33:00 +0200
Subject: [PATCH] glib: fix docs cross compilation (again)

Do not depend on host gtk-doc when cross compiling (we do not use it
there), and document why we need a host gtk-doc in the first place.
---
 pkgs/development/libraries/glib/default.nix | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/pkgs/development/libraries/glib/default.nix b/pkgs/development/libraries/glib/default.nix
index ce64bef95ad..fccd6ddb041 100644
--- a/pkgs/development/libraries/glib/default.nix
+++ b/pkgs/development/libraries/glib/default.nix
@@ -92,13 +92,23 @@ stdenv.mkDerivation rec {
   buildInputs = [
     libelf setupHook pcre
     bash gnum4 # install glib-gettextize and m4 macros for other apps to use
-    gtk-doc
   ] ++ optionals stdenv.isLinux [
     libselinux
     util-linuxMinimal # for libmount
   ] ++ optionals stdenv.isDarwin (with darwin.apple_sdk.frameworks; [
     AppKit Carbon Cocoa CoreFoundation CoreServices Foundation
-  ]);
+  ]) ++ optionals (stdenv.hostPlatform == stdenv.buildPlatform) [
+    # Note: this needs to be both in buildInputs and nativeBuildInputs. The
+    # Meson gtkdoc module uses find_program to look it up (-> build dep), but
+    # glib's own Meson configuration uses the host pkg-config to find its
+    # version (-> host dep). We could technically go and fix this in glib, add
+    # pkg-config to depsBuildBuild, but this would be a futile exercise since
+    # Meson's gtkdoc integration does not support cross compilation[1] anyway
+    # and this derivation disables the docs build when cross compiling.
+    #
+    # [1] https://github.com/mesonbuild/meson/issues/2003
+    gtk-doc
+  ];
 
   strictDeps = true;