From 4035c1ad059d5cab76b8322aed55e79b02c0cebf Mon Sep 17 00:00:00 2001
From: benaryorg <binary@benary.org>
Date: Thu, 7 Nov 2024 03:46:23 +0000
Subject: [PATCH] phash: compilation fixes

This includes a patch already sent upstream that fixes compilation with Werror due to a lacking return, as well as adding a linker flag to include a threaded version of a library.
The fftw3_threads part stems from cimg requiring this apparently when linking the examples:

> test_texthash.cpp:(.text.startup+0x1c1): undefined reference to `fftw_init_threads'

I wouldn't know how to patch this upstream, however other packages in nixpkgs seem to provide the LDFLAGS too.

Signed-off-by: benaryorg <binary@benary.org>
---
 .../0001-proper-pthread-return-value.patch    | 40 +++++++++++++++++++
 pkgs/by-name/ph/phash/package.nix             |  9 ++++-
 2 files changed, 48 insertions(+), 1 deletion(-)
 create mode 100644 pkgs/by-name/ph/phash/0001-proper-pthread-return-value.patch

diff --git a/pkgs/by-name/ph/phash/0001-proper-pthread-return-value.patch b/pkgs/by-name/ph/phash/0001-proper-pthread-return-value.patch
new file mode 100644
index 000000000000..52e929e57951
--- /dev/null
+++ b/pkgs/by-name/ph/phash/0001-proper-pthread-return-value.patch
@@ -0,0 +1,40 @@
+From 6ac2f207e8d8e1d16ee73198abccc64d20c5f608 Mon Sep 17 00:00:00 2001
+From: benaryorg <binary@benary.org>
+Date: Thu, 7 Nov 2024 03:27:52 +0000
+Subject: [PATCH 1/2] proper pthread return value
+
+*pthread_create(3)* states that the ways for a pthread to exit includes:
+
+> It returns from start_routine().  This is equivalent to calling pthread_exit(3) with the value supplied in the return statement.
+
+This "retval" is a void pointer which can be anything.
+In this case, since all threads are always joined with a parameter of NULL for the `void**` to store the retval this isn't really relevant for providing a meaningful return value.
+However a `void*` function must return a `void*`, otherwise compilers will complain:
+
+> pHash.cpp:416:1: warning: no return statement in function returning non-void [8;;https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wreturn-type-Wreturn-type8;;]
+
+Therefore returning NULL seems reasonable.
+As for the choice of NULL vs. nullptr or any other value, NULL is already widely used in the file.
+
+Long story short: this fixes a compiler warning/error.
+
+Signed-off-by: benaryorg <binary@benary.org>
+---
+ src/pHash.cpp | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/src/pHash.cpp b/src/pHash.cpp
+index 07b03ad..23bbbf3 100644
+--- a/src/pHash.cpp
++++ b/src/pHash.cpp
+@@ -417,6 +417,7 @@ void *ph_image_thread(void *p)
+ 		memcpy(dp->hash, &hash, sizeof(hash));
+                 dp->hash_length = 1;
+         }
++        return NULL;
+ }
+ 
+ DP** ph_dct_image_hashes(char *files[], int count, int threads)
+-- 
+2.44.1
+
diff --git a/pkgs/by-name/ph/phash/package.nix b/pkgs/by-name/ph/phash/package.nix
index 73097db5ccc6..8f40cd0d9a71 100644
--- a/pkgs/by-name/ph/phash/package.nix
+++ b/pkgs/by-name/ph/phash/package.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchFromGitHub, pkg-config, cimg, imagemagick }:
+{ lib, stdenv, fetchFromGitHub, fetchpatch, pkg-config, cimg, imagemagick }:
 
 stdenv.mkDerivation rec {
   pname = "pHash";
@@ -24,6 +24,13 @@ stdenv.mkDerivation rec {
     sha256 = "sha256-frISiZ89ei7XfI5F2nJJehfQZsk0Mlb4n91q/AiZ2vA=";
   };
 
+  NIX_LDFLAGS = "-lfftw3_threads";
+
+  patches = [
+    # proper pthread return value (https://github.com/clearscene/pHash/pull/20)
+    ./0001-proper-pthread-return-value.patch
+  ];
+
   meta = with lib; {
     description = "Compute the perceptual hash of an image";
     license = licenses.gpl3;