postgresql: split dev output

This splits a dev output to make the default output not depend on any
build dependencies anymore. This also avoids removing references from
pgxs' Makefile this way, which should, at least theoretically, be good
to build extensions via pgxs, making sure they use the same tooling.

ecpg is the "embedded SQL C preprocessor", which is certainly a dev tool.

Most important, for closure size anyway, is to move pg_config to the dev
output, since it retains paths to all the other outputs.

The only thing with references to the dev output remaining is then the
postgres binary itself. It contains all the output paths, because it
shows those in the pg_config system view. There is no other way than
to nuke those references to avoid circular dependencies between outputs -
and blowing up closure size again.

Overall this reduces the closure for v15 by about 12-13 MB. That's all we
can get, because no build dependencies remain.

pkgs/servers/sql/postgresql/generic.nix

@@ -6,6 +6,7 @@ let
       , glibc, zlib, readline, openssl, icu, lz4, zstd, systemd, libossp_uuid
       , pkg-config, libxml2, tzdata, libkrb5, substituteAll, darwin
       , linux-pam
+      , removeReferencesTo
 
       # This is important to obtain a version of `libpq` that does not depend on systemd.
       , systemdSupport ? lib.meta.availableOn stdenv.hostPlatform systemd && !stdenv.hostPlatform.isStatic
@@ -66,10 +67,24 @@ let
 
     hardeningEnable = lib.optionals (!stdenv'.cc.isClang) [ "pie" ];
 
-    outputs = [ "out" "lib" "doc" "man" ];
-    setOutputFlags = false; # $out retains configureFlags :-/
+    outputs = [ "out" "dev" "doc" "lib" "man" ];
+    outputChecks.out = {
+      disallowedReferences = [ "dev" "doc" "man" ];
+      disallowedRequisites = [
+        stdenv'.cc
+      ] ++ lib.optionals jitSupport [
+        llvmPackages.llvm.out
+        llvmPackages.llvm.dev
+      ];
+    };
     outputChecks.lib = {
-      disallowedReferences = [ "out" "doc" "man" ];
+      disallowedReferences = [ "out" "dev" "doc" "man" ];
+      disallowedRequisites = [
+        stdenv'.cc
+      ] ++ lib.optionals jitSupport [
+        llvmPackages.llvm.out
+        llvmPackages.llvm.dev
+      ];
     };
 
     buildInputs = [
@@ -92,6 +107,7 @@ let
     nativeBuildInputs = [
       makeWrapper
       pkg-config
+      removeReferencesTo
     ]
       ++ lib.optionals jitSupport [ llvmPackages.llvm.dev nukeReferences patchelf ];
 
@@ -122,7 +138,6 @@ let
       "--with-libxml"
       "--with-icu"
       "--sysconfdir=/etc"
-      "--libdir=$(lib)/lib"
       "--with-system-tzdata=${tzdata}/share/zoneinfo"
       "--enable-debug"
       (lib.optionalString systemdSupport' "--with-systemd")
@@ -158,43 +173,45 @@ let
 
     postPatch = ''
       substituteInPlace "src/Makefile.global.in" --subst-var out
-      # Hardcode the path to pgxs so pg_config returns the path in $out
-      substituteInPlace "src/common/config_info.c" --subst-var out
+      # Hardcode the path to pgxs so pg_config returns the path in $dev
+      substituteInPlace "src/common/config_info.c" --subst-var dev
     '';
 
     postInstall =
       ''
-        moveToOutput "lib/libpgcommon*.a" "$out"
-        moveToOutput "lib/libpgport*.a" "$out"
-
-        # Prevent a retained dependency on gcc-wrapper.
-        substituteInPlace "$out/lib/pgxs/src/Makefile.global" --replace ${stdenv'.cc}/bin/ld ld
+        moveToOutput "bin/ecpg" "$dev"
+        moveToOutput "lib/pgxs" "$dev"
+
+        # Pretend pg_config is located in $out/bin to return correct paths, but
+        # actually have it in -dev to avoid pulling in all other outputs.
+        moveToOutput "bin/pg_config" "$dev"
+        touch "$out/bin/pg_config" && chmod +x "$out/bin/pg_config"
+        wrapProgram "$dev/bin/pg_config" --argv0 "$out/bin/pg_config"
+
+        # postgres shows all the configured paths in the pg_config view.
+        # To prevent reference cycles between outputs, the paths to the
+        # dev, doc and man outputs will be removed from that view.
+        # References to the lib output are kept, because that output is linked
+        # to from allmost all other binaries anyway - many of them use libpq.
+        remove-references-to -t "$dev" -t "$doc" -t "$man" "$out/bin/postgres"
 
         if [ -z "''${dontDisableStatic:-}" ]; then
           # Remove static libraries in case dynamic are available.
-          for i in $out/lib/*.a $lib/lib/*.a; do
+          for i in $lib/lib/*.a; do
             name="$(basename "$i")"
             ext="${stdenv'.hostPlatform.extensions.sharedLibrary}"
             if [ -e "$lib/lib/''${name%.a}$ext" ] || [ -e "''${i%.a}$ext" ]; then
               rm "$i"
             fi
           done
         fi
+        # The remaining static libraries are libpgcommon.a, libpgport.a and related.
+        # Those are only used when building e.g. extensions, so go to $dev.
+        moveToOutput "lib/*.a" "$dev"
       '' + lib.optionalString jitSupport ''
         # In the case of JIT support, prevent a retained dependency on clang-wrapper
-        substituteInPlace "$out/lib/pgxs/src/Makefile.global" --replace ${stdenv'.cc}/bin/clang clang
         nuke-refs $out/lib/llvmjit_types.bc $(find $out/lib/bitcode -type f)
 
-        # Stop out depending on the default output of llvm
-        substituteInPlace $out/lib/pgxs/src/Makefile.global \
-          --replace ${llvmPackages.llvm.out}/bin "" \
-          --replace '$(LLVM_BINPATH)/' ""
-
-        # Stop out depending on the -dev output of llvm
-        substituteInPlace $out/lib/pgxs/src/Makefile.global \
-          --replace ${llvmPackages.llvm.dev}/bin/llvm-config llvm-config \
-          --replace -I${llvmPackages.llvm.dev}/include ""
-
         ${lib.optionalString (!stdenv'.isDarwin) ''
           # Stop lib depending on the -dev output of llvm
           rpath=$(patchelf --print-rpath $out/lib/llvmjit.so)
@@ -214,8 +231,6 @@ let
     # autodetection doesn't seem to able to find this, but it's there.
     checkTarget = "check";
 
-    disallowedReferences = [ stdenv'.cc ];
-
     passthru = let
       this = self.callPackage generic args;
       jitToggle = this.override {

pkgs/servers/sql/postgresql/patches/paths-for-split-outputs.patch

@@ -4,7 +4,7 @@
  	i++;
 
  	configdata[i].name = pstrdup("PGXS");
-+	strlcpy(path, "@out@/lib", sizeof(path));
++	strlcpy(path, "@dev@/lib", sizeof(path));
 -	get_pkglib_path(my_exec_path, path);
  	strlcat(path, "/pgxs/src/makefiles/pgxs.mk", sizeof(path));
  	cleanup_path(path);