phash: compilation fixes (#354135)

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

{ lib, stdenv, fetchFromGitHub, pkg-config, cimg, imagemagick }:

{ lib, stdenv, fetchFromGitHub, fetchpatch, pkg-config, cimg, imagemagick }:

stdenv.mkDerivation rec {

  pname = "pHash";

    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;