Bug#1140755: clang-21: Uninstallable for cross builds

[Yavor Doganov]

Package: clang-21
Version: 1:21.1.8-7+b3
Tags: patch
User: debian-cross at lists.debian.org
Usertags: cross-satisfiability

Packages that build-depend on clang cannot be cross built because
bin:clang from src:llvm-defaults depends on bin:clang-$MAJORVER which
in turn depends on binutils.  I used the attached patch to build
llvm-toolchain-21 on arm64/s390x.  Then I used the produced binary
packages and successfully cross built (on amd64 for arm64/s390x) a
bunch of packages that build-depend on clang, including the package
I'm interested in, libobjc2 (not yet in Debian).

We at the GNUstep team plan to package the GNUstep Objective-C runtime
which was specifically written for Clang, and to provide dual runtime
support on architectures where it will be available.  We've spent
considerable efforts to make the GNUstep stack cross-buildable during
the trixie release cycle and it would be a pity to lose that feature.

In case you consider applying the patch, the same should be done for
other (relevant) llvm-toolchain-* packages.  Thanks.

P.S.: I see that some packages (e.g., filament) build-depend on
clang:native, have a cross-specific make conditional in debian/rules
and pass --target accordingly.  This won't work in our case because
bin:gnustep-make must depend on clang and the :native annotation can
be used only for build-dependencies, IIRC.
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>From b9616f0212f5becf511b36e68d6769701c727884 Mon Sep 17 00:00:00 2001
From: Yavor Doganov <yavor at gnu.org>
Date: Thu, 25 Jun 2026 23:51:03 +0300
Subject: [PATCH] Make clang-21 depend on binutils-for-host instead of binutils

---
 debian/changelog  | 4 ++++
 debian/control    | 2 +-
 debian/control.in | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/debian/changelog b/debian/changelog
index bf26acc5..e6fdf658 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -22,6 +22,10 @@ llvm-toolchain-21 (1:21.1.8-8) UNRELEASED; urgency=medium
     clang-21-doc package. Without them, clang-doc fails with "default
     index.js file missing at .../share/clang-doc/index.js".
 
+  [ Yavor Doganov ]
+  * d/control: Let clang-21 depend on binutils-for-host instead of
+    binutils so that it's installable for cross builds (Closes: #-1).
+
  -- Matthias Klose <doko at debian.org>  Sat, 09 May 2026 09:55:55 +0200
 
 llvm-toolchain-21 (1:21.1.8-7) unstable; urgency=medium
diff --git a/debian/control b/debian/control
index 3564589e..12524e44 100644
--- a/debian/control
+++ b/debian/control
@@ -50,7 +50,7 @@ Depends: ${shlibs:Depends}, ${misc:Depends}, ${dep:devlibs},
  libllvm21 (= ${binary:Version}),
  libclang-common-21-dev (= ${binary:Version}),
  llvm-21-linker-tools (= ${binary:Version}),
- libclang1-21 (= ${binary:Version}), libc6-dev, binutils
+ libclang1-21 (= ${binary:Version}), libc6-dev, binutils-for-host
 Provides: c-compiler, objc-compiler, c++-compiler, objc++-compiler
 Recommends: llvm-21-dev, python3, clang-tools-21
 # libomp-21-dev
diff --git a/debian/control.in b/debian/control.in
index 7a6bd011..e4c8f4ae 100644
--- a/debian/control.in
+++ b/debian/control.in
@@ -50,7 +50,7 @@ Depends: ${shlibs:Depends}, ${misc:Depends}, ${dep:devlibs},
  libllvm at LLVM_VERSION@ (= ${binary:Version}),
  libclang-common- at LLVM_VERSION@-dev (= ${binary:Version}),
  llvm- at LLVM_VERSION@-linker-tools (= ${binary:Version}),
- libclang1- at LLVM_VERSION@ (= ${binary:Version}), libc6-dev, binutils
+ libclang1- at LLVM_VERSION@ (= ${binary:Version}), libc6-dev, binutils-for-host
 Provides: c-compiler, objc-compiler, c++-compiler, objc++-compiler
 Recommends: llvm- at LLVM_VERSION@-dev, python3, clang-tools- at LLVM_VERSION@
 # libomp- at LLVM_VERSION@-dev
-- 
2.53.0