pyrox.dev
1# Platform Notes {#chap-platform-notes}
2
3## Darwin (macOS) {#sec-darwin}
4
5Some common issues when packaging software for Darwin:
6
7- The Darwin `stdenv` uses clang instead of gcc. When referring to the compiler `$CC` or `cc` will work in both cases. Some builds hardcode gcc/g++ in their build scripts, that can usually be fixed with using something like `makeFlags = [ "CC=cc" ];` or by patching the build scripts.
8
9 ```nix
10 stdenv.mkDerivation {
11 name = "libfoo-1.2.3";
12 # ...
13 buildPhase = ''
14 $CC -o hello hello.c
15 '';
16 }
17 ```
18
19- On Darwin, libraries are linked using absolute paths, libraries are resolved by their `install_name` at link time. Sometimes packages won’t set this correctly causing the library lookups to fail at runtime. This can be fixed by adding extra linker flags or by running `install_name_tool -id` during the `fixupPhase`.
20
21 ```nix
22 stdenv.mkDerivation {
23 name = "libfoo-1.2.3";
24 # ...
25 makeFlags = lib.optional stdenv.isDarwin "LDFLAGS=-Wl,-install_name,$(out)/lib/libfoo.dylib";
26 }
27 ```
28
29- Even if the libraries are linked using absolute paths and resolved via their `install_name` correctly, tests can sometimes fail to run binaries. This happens because the `checkPhase` runs before the libraries are installed.
30
31 This can usually be solved by running the tests after the `installPhase` or alternatively by using `DYLD_LIBRARY_PATH`. More information about this variable can be found in the *dyld(1)* manpage.
32
33 ```
34 dyld: Library not loaded: /nix/store/7hnmbscpayxzxrixrgxvvlifzlxdsdir-jq-1.5-lib/lib/libjq.1.dylib
35 Referenced from: /private/tmp/nix-build-jq-1.5.drv-0/jq-1.5/tests/../jq
36 Reason: image not found
37 ./tests/jqtest: line 5: 75779 Abort trap: 6
38 ```
39
40 ```nix
41 stdenv.mkDerivation {
42 name = "libfoo-1.2.3";
43 # ...
44 doInstallCheck = true;
45 installCheckTarget = "check";
46 }
47 ```
48
49- Some packages assume xcode is available and use `xcrun` to resolve build tools like `clang`, etc. This causes errors like `xcode-select: error: no developer tools were found at '/Applications/Xcode.app'` while the build doesn’t actually depend on xcode.
50
51 ```nix
52 stdenv.mkDerivation {
53 name = "libfoo-1.2.3";
54 # ...
55 prePatch = ''
56 substituteInPlace Makefile \
57 --replace-fail '/usr/bin/xcrun clang' clang
58 '';
59 }
60 ```
61
62 The package `xcbuild` can be used to build projects that really depend on Xcode. However, this replacement is not 100% compatible with Xcode and can occasionally cause issues.
63
64- x86_64-darwin uses the 10.12 SDK by default, but some software is not compatible with that version of the SDK. In that case,
65 the 11.0 SDK used by aarch64-darwin is available for use on x86_64-darwin. To use it, reference `apple_sdk_11_0` instead of
66 `apple_sdk` in your derivation and use `pkgs.darwin.apple_sdk_11_0.callPackage` instead of `pkgs.callPackage`. On Linux, this will
67 have the same effect as `pkgs.callPackage`, so you can use `pkgs.darwin.apple_sdk_11_0.callPackage` regardless of platform.