From 8f41fb68ff7443836f280323674a6a4a5e7fa0a3 Mon Sep 17 00:00:00 2001
From: Felix Uhl <github@mail.felix-uhl.de>
Date: Wed, 6 Mar 2024 00:18:24 +0100
Subject: [PATCH] zsync: fix build with clang

I originally found the fix in [this HomeBrew
formula](https://github.com/Homebrew/homebrew-core/blob/f800f85efed9312a1abc5fcf7f1269576a3f2d95/Formula/z/zsync.rb#L32).

I tested the built binary like this:

    zsync http://cdimage.ubuntu.com/ubuntu/daily-live/current/noble-desktop-amd64.iso.zsync

Aborting the download and starting it again worked, it continued at
the same percentage mark. So I'm very certain that the compilation
error really is a mistake, and suppressing it is not an issue.
---
 pkgs/tools/compression/zsync/default.nix | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/pkgs/tools/compression/zsync/default.nix b/pkgs/tools/compression/zsync/default.nix
index 0de21cb9c736..94aa7acce2e0 100644
--- a/pkgs/tools/compression/zsync/default.nix
+++ b/pkgs/tools/compression/zsync/default.nix
@@ -9,6 +9,12 @@ stdenv.mkDerivation rec {
     sha256 = "1wjslvfy76szf0mgg2i9y9q30858xyjn6v2acc24zal76d1m778b";
   };
 
+  env = lib.optionalAttrs stdenv.cc.isClang {
+    # Suppress error "call to undeclared library function 'strcasecmp'" during compilation.
+    # The function is found by the linker correctly, so this doesn't introduce any issues.
+    NIX_CFLAGS_COMPILE = " -Wno-implicit-function-declaration";
+  };
+
   makeFlags = [ "AR=${stdenv.cc.bintools.targetPrefix}ar" ];
 
   meta = with lib; {