allow fetchpatch everywhere, without restrictions

pkgs/build-support/fetchurl/boot.nix

@@ -1,20 +1,25 @@
 let mirrors = import ./mirrors.nix; in
 
-{ system }:
+{ system
+, stdenv
+, fetchurl }:
 
 { url ? builtins.head urls
 , urls ? []
 , sha256 ? ""
 , hash ? ""
 , name ? baseNameOf (toString url)
-}:
+, __impure ? false
+, postFetch ? null
+}@args:
 
-# assert exactly one hash is set
-assert hash != "" || sha256 != "";
+# assert at most one hash is set
 assert hash != "" -> sha256 == "";
+assert sha256 != "" -> hash == "";
 
-import <nix/fetchurl.nix> {
-  inherit system hash sha256 name;
+if postFetch==null
+then import <nix/fetchurl.nix> {
+  inherit system hash sha256 name __impure;
 
   url =
     # Handle mirror:// URIs. Since <nix/fetchurl.nix> currently
@@ -23,3 +28,21 @@ import <nix/fetchurl.nix> {
     if m == null then url
     else builtins.head (mirrors.${builtins.elemAt m 0}) + (builtins.elemAt m 1);
 }
+else stdenv.mkDerivation {
+  inherit name;
+  srcs = [ ];
+  unpackPhase = ''
+    runHook preUnpack
+    cp '${fetchurl (args // { postFetch=null; hash=""; sha256=""; __impure=true; })}' $out
+    chmod +w $out
+    runHook postUnpack
+  '';
+  installPhase = ''
+    runHook preInstall
+  '' + postFetch + ''
+    runHook postInstall
+  '';
+  outputHash = if hash != "" then hash else sha256;
+  outputHashAlgo = if hash != "" then "" else "sha256";
+  outputHashMode = "flat";
+}

pkgs/development/tools/misc/binutils/default.nix

@@ -9,6 +9,7 @@ in
 , buildPackages
 , fetchFromGitHub
 , fetchurl
+, fetchpatch
 , flex
 , gettext
 , lib
@@ -68,11 +69,26 @@ stdenv.mkDerivation {
     # Make binutils output deterministic by default.
     ./deterministic.patch
 
-
     # Breaks nm BSD flag detection, heeds an upstream fix:
     #   https://sourceware.org/PR29547
     ./0001-Revert-libtool.m4-fix-the-NM-nm-over-here-B-option-w.patch
-    ./0001-Revert-libtool.m4-fix-nm-BSD-flag-detection.patch
+
+    # If the following patch is ever dropped, please ensure that at
+    # least one other patch in binutils uses `fetchpatch`, and move
+    # this comment to that patch.  Having a `fetchpatch` in binutils
+    # serves as a regression test to ensure that there are no
+    # dependency cycles preventing it from being used in even the
+    # earliest stages of stdenv bootstrapping.
+    (fetchpatch {
+      # Breaks nm BSD flag detection
+      name = "0001-Revert-libtool.m4-fix-nm-BSD-flag-detection.patch";
+      url = "https://sourceware.org/git/?p=binutils-gdb.git;a=patch;h=bef9ef8ca0f941d743c77cc55b5fe7985990b2a7";
+      revert = true;
+      excludes = [ "ChangeLog" ];
+      #hash = "sha256-VQyyPmY1P9NT7PYwu0vqocWmQGSyt45tADe6ecTc8fk=";
+      hash = "sha256-FcTkFK9FfbgDR6iS+H6w7KRpPo/mFJ+0u7v5EvIlecQ=";
+    })
+    #./0001-Revert-libtool.m4-fix-nm-BSD-flag-detection.patch
 
     # Required for newer macos versions
     ./0001-libtool.m4-update-macos-version-detection-block.patch

pkgs/stdenv/darwin/default.nix

@@ -186,6 +186,8 @@ rec {
 
         fetchurlBoot = import ../../build-support/fetchurl {
           inherit lib;
+          inherit (prevStage) stdenv;
+          fetchurl = thisStdenv.fetchurlBoot;
           stdenvNoCC = stage0.stdenv;
           curl = bootstrapTools;
         };
@@ -208,6 +210,18 @@ rec {
 
   stage0 = stageFun 0 null {
     overrides = self: super: with stage0; {
+
+      fetchpatch = import ../../build-support/fetchpatch/default.nix {
+        inherit lib;
+        buildPackages.patchutils_0_3_3 = prevStage.patchutils_0_3_3.override {
+          forStdenvBootstrap = true;
+          # the parts of patchutils used by fetchpatch do not
+          # require perl, so we could eliminate this by patching
+          # patchutils' build scripts...
+          perl = bootstrapTools;
+        };
+      };
+
       coreutils = stdenv.mkDerivation {
         name = "bootstrap-stage0-coreutils";
         buildCommand = ''

pkgs/stdenv/linux/default.nix

@@ -104,6 +104,8 @@ let
 
         fetchurlBoot = import ../../build-support/fetchurl/boot.nix {
           inherit system;
+          inherit (prevStage) stdenv;
+          fetchurl = thisStdenv.fetchurlBoot;
         };
 
         cc = if prevStage.gcc-unwrapped == null
@@ -188,6 +190,17 @@ in
       };
       coreutils = bootstrapTools;
       gnugrep = bootstrapTools;
+
+      fetchpatch = import ../../build-support/fetchpatch/default.nix {
+        inherit lib;
+        buildPackages.patchutils_0_3_3 = prevStage.patchutils_0_3_3.override {
+          forStdenvBootstrap = true;
+          # the parts of patchutils used by fetchpatch do not
+          # require perl, so we could eliminate this by patching
+          # patchutils' build scripts...
+          perl = bootstrapTools;
+        };
+      };
     };
   })
 

pkgs/tools/text/patchutils/generic.nix

@@ -1,5 +1,6 @@
 { lib, stdenv, fetchurl, perl, makeWrapper
 , version, sha256, patches ? [], extraBuildInputs ? []
+, forStdenvBootstrap ? false
 , ...
 }:
 stdenv.mkDerivation rec {
@@ -11,14 +12,14 @@ stdenv.mkDerivation rec {
     inherit sha256;
   };
 
-  nativeBuildInputs = [ makeWrapper ];
+  nativeBuildInputs = lib.optionals (!forStdenvBootstrap) [ makeWrapper ];
   buildInputs = [ perl ] ++ extraBuildInputs;
   hardeningDisable = [ "format" ];
 
   # tests fail when building in parallel
   enableParallelBuilding = false;
 
-  postInstall = ''
+  postInstall = lib.optionalString (!forStdenvBootstrap) ''
     for bin in $out/bin/{splitdiff,rediff,editdiff,dehtmldiff}; do
       wrapProgram "$bin" \
         --prefix PATH : "$out/bin"