diff --git a/pkgs/development/compilers/gcc/7/default.nix b/pkgs/development/compilers/gcc/7/default.nix
index a0465e8bdd60..d22e85c61adc 100644
--- a/pkgs/development/compilers/gcc/7/default.nix
+++ b/pkgs/development/compilers/gcc/7/default.nix
@@ -165,33 +165,29 @@ stdenv.mkDerivation ({
   inherit noSysDirs staticCompiler crossStageStatic
     libcCross crossMingw;
 
-  depsBuildBuild = [ buildPackages.stdenv.cc ];
-  nativeBuildInputs = [ texinfo which gettext ]
-    ++ (optional (perl != null) perl)
-    # The builder relies on GNU sed (for instance, Darwin's `sed' fails with
-    # "-i may not be used with stdin"), and `stdenvNative' doesn't provide it.
-    ++ (optional buildPlatform.isDarwin gnused)
+  inherit (import ../common/dependencies.nix {
+    inherit
+      lib
+      stdenv
+      buildPackages
+      targetPackages
+      crossStageStatic
+      threadsCross
+      version
+      texinfo
+      which
+      gettext
+      gnused
+      patchelf
+      gmp
+      mpfr
+      libmpc
+      isl
+      zlib
+      zip
+      perl
     ;
-
-  # For building runtime libs
-  depsBuildTarget =
-    (
-      if hostPlatform == buildPlatform then [
-        targetPackages.stdenv.cc.bintools # newly-built gcc will be used
-      ] else assert targetPlatform == hostPlatform; [ # build != host == target
-        stdenv.cc
-      ]
-    )
-    ++ optional targetPlatform.isLinux patchelf;
-
-  buildInputs = [
-    gmp mpfr libmpc
-    targetPackages.stdenv.cc.bintools # For linking code at run-time
-  ] ++ (optional (isl != null) isl)
-    ++ (optional (zlib != null) zlib)
-    ;
-
-  depsTargetTarget = optional (!crossStageStatic && threadsCross != {}) threadsCross.package;
+  }) depsBuildBuild nativeBuildInputs depsBuildTarget buildInputs depsTargetTarget;
 
   NIX_CFLAGS_COMPILE = lib.optionalString (stdenv.cc.isClang && langFortran) "-Wno-unused-command-line-argument";
   NIX_LDFLAGS = lib.optionalString  hostPlatform.isSunOS "-lm -ldl";
diff --git a/pkgs/development/compilers/gcc/8/default.nix b/pkgs/development/compilers/gcc/8/default.nix
index 03fb9fb1205c..2b43fc124bf0 100644
--- a/pkgs/development/compilers/gcc/8/default.nix
+++ b/pkgs/development/compilers/gcc/8/default.nix
@@ -147,33 +147,29 @@ stdenv.mkDerivation ({
   inherit noSysDirs staticCompiler crossStageStatic
     libcCross crossMingw;
 
-  depsBuildBuild = [ buildPackages.stdenv.cc ];
-  nativeBuildInputs = [ texinfo which gettext ]
-    ++ (optional (perl != null) perl)
-    # The builder relies on GNU sed (for instance, Darwin's `sed' fails with
-    # "-i may not be used with stdin"), and `stdenvNative' doesn't provide it.
-    ++ (optional buildPlatform.isDarwin gnused)
+  inherit (import ../common/dependencies.nix {
+    inherit
+      lib
+      stdenv
+      buildPackages
+      targetPackages
+      crossStageStatic
+      threadsCross
+      version
+      texinfo
+      which
+      gettext
+      gnused
+      patchelf
+      gmp
+      mpfr
+      libmpc
+      isl
+      zlib
+      zip
+      perl
     ;
-
-  # For building runtime libs
-  depsBuildTarget =
-    (
-      if hostPlatform == buildPlatform then [
-        targetPackages.stdenv.cc.bintools # newly-built gcc will be used
-      ] else assert targetPlatform == hostPlatform; [ # build != host == target
-        stdenv.cc
-      ]
-    )
-    ++ optional targetPlatform.isLinux patchelf;
-
-  buildInputs = [
-    gmp mpfr libmpc
-    targetPackages.stdenv.cc.bintools # For linking code at run-time
-  ] ++ (optional (isl != null) isl)
-    ++ (optional (zlib != null) zlib)
-    ;
-
-  depsTargetTarget = optional (!crossStageStatic && threadsCross != {}) threadsCross.package;
+  }) depsBuildBuild nativeBuildInputs depsBuildTarget buildInputs depsTargetTarget;
 
   NIX_LDFLAGS = lib.optionalString  hostPlatform.isSunOS "-lm -ldl";
 
diff --git a/pkgs/development/compilers/gcc/common/dependencies.nix b/pkgs/development/compilers/gcc/common/dependencies.nix
index 8bb794bf2359..2890ee298112 100644
--- a/pkgs/development/compilers/gcc/common/dependencies.nix
+++ b/pkgs/development/compilers/gcc/common/dependencies.nix
@@ -6,7 +6,7 @@
 , texinfo
 , which
 , gettext
-, pkg-config
+, pkg-config ? null
 , gnused
 , patchelf
 , gmp
@@ -17,11 +17,11 @@
 , zlib ? null
 , gnatboot ? null
 , flex ? null
-, boehmgc
-, zip
-, unzip
-, gtk2
-, libart_lgpl
+, boehmgc ? null
+, zip ? null
+, unzip ? null
+, gtk2 ? null
+, libart_lgpl ? null
 , perl ? null
 , xlibs ? null
 , langJava ? false
@@ -47,7 +47,7 @@ in
   ]
   ++ optionals (perl != null) [ perl ]
   ++ optionals javaAwtGtk [ pkg-config ]
-  ++ optionals (with stdenv.targetPlatform; isVc4 || isRedox) [ flex ]
+  ++ optionals (with stdenv.targetPlatform; isVc4 || isRedox && flex != null) [ flex ]
   ++ optionals langAda [ gnatboot ]
   # The builder relies on GNU sed (for instance, Darwin's `sed' fails with
   # "-i may not be used with stdin"), and `stdenvNative' doesn't provide it.