* Linker accepts a name for the program.

* Better diagnostics.

examples/not-so-simple-header/default.nix

@@ -2,7 +2,7 @@ let {
 
   inherit (import ../../lib) compileC link;
 
-  hello = link {objects = compileC {
+  hello = link {programName = "hello"; objects = compileC {
     main = ./foo/hello.c;
     localIncludes = [
       [./foo/fnord/indirect.h "fnord/indirect.h"]

lib/compile-c.sh

@@ -2,7 +2,7 @@
 
 mainName=$(basename $main | cut -c34-)
 
-echo "compiling $mainName..."
+echo "compiling \`$mainName'..."
 
 # Turn $localIncludes into an array.
 localIncludes=($localIncludes)
@@ -67,4 +67,5 @@ done
 ln -s $main $prefix$mainName
 
 mkdir $out
-gcc -Wall -c $prefix$mainName -o $out/$mainName.o
+test "$prefix" && cd $prefix
+gcc -Wall -c $mainName -o $out/$mainName.o

lib/default.nix

@@ -8,10 +8,10 @@ rec {
     inherit main localIncludes;
   };
 
-  link = {objects}: stdenv.mkDerivation {
+  link = {objects, programName ? "program"}: stdenv.mkDerivation {
     name = "link";
     builder = ./link.sh;
-    inherit objects;
+    inherit objects programName;
   };
   
 }

lib/link.sh

@@ -2,9 +2,11 @@
 
 objs=
 for i in "$objects"; do
-    obj=$i/*.o
+    obj=$(echo $i/*.o)
     objs="$objs $obj"
 done
 
+echo "linking object files into \`$programName'..."
+
 mkdir $out
-gcc -o $out/program $objs
+gcc -o $out/$programName $objs