libredirect: Add support for Darwin

pkgs/build-support/libredirect/default.nix

@@ -1,19 +1,41 @@
-{ stdenv }:
+{ stdenv, coreutils }:
 
 stdenv.mkDerivation {
   name = "libredirect-0";
 
-  unpackPhase = "cp ${./libredirect.c} libredirect.c";
+  unpackPhase = ''
+    cp ${./libredirect.c} libredirect.c
+    cp ${./test.c} test.c
+  '';
 
-  buildPhase =
-    ''
-      gcc -Wall -std=c99 -O3 -shared libredirect.c -o libredirect.so -fPIC -ldl
-    '';
+  shlibext = stdenv.targetPlatform.extensions.sharedLibrary;
+
+  buildPhase = ''
+    $CC -Wall -std=c99 -O3 -shared libredirect.c \
+      -o "libredirect$shlibext" -fPIC -ldl
+
+    if [ -n "$doInstallCheck" ]; then
+      $CC -Wall -std=c99 -O3 test.c -o test
+    fi
+  '';
+
+  installPhase = ''
+    install -vD "libredirect$shlibext" "$out/lib/libredirect$shlibext"
+  '';
+
+  doInstallCheck = true;
 
-  installPhase = "mkdir -p $out/lib; cp libredirect.so $out/lib";
+  installCheckPhase = if stdenv.isDarwin then ''
+    NIX_REDIRECTS="/foo/bar/test=${coreutils}/bin/true" \
+    DYLD_INSERT_LIBRARIES="$out/lib/libredirect$shlibext" \
+    DYLD_FORCE_FLAT_NAMESPACE=1 ./test
+  '' else ''
+    NIX_REDIRECTS="/foo/bar/test=${coreutils}/bin/true" \
+    LD_PRELOAD="$out/lib/libredirect$shlibext" ./test
+  '';
 
   meta = {
-    platforms = stdenv.lib.platforms.linux;
+    platforms = stdenv.lib.platforms.unix;
     description = "An LD_PRELOAD library to intercept and rewrite the paths in glibc calls";
     longDescription = ''
       libredirect is an LD_PRELOAD library to intercept and rewrite the paths in

pkgs/build-support/libredirect/test.c

@@ -0,0 +1,59 @@
+#include <assert.h>
+#include <fcntl.h>
+#include <spawn.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#define TESTPATH "/foo/bar/test"
+
+extern char **environ;
+
+void test_spawn(void) {
+    pid_t pid;
+    int ret;
+    posix_spawn_file_actions_t file_actions;
+    char *argv[] = {"true", NULL};
+
+    assert(posix_spawn_file_actions_init(&file_actions) == 0);
+
+    ret = posix_spawn(&pid, TESTPATH, &file_actions, NULL, argv, environ);
+
+    assert(ret == 0);
+    assert(waitpid(pid, NULL, 0) != -1);
+}
+
+void test_execv(void) {
+    char *argv[] = {"true", NULL};
+    assert(execv(TESTPATH, argv) == 0);
+}
+
+int main(void)
+{
+    FILE *testfp;
+    int testfd;
+    struct stat testsb;
+
+    testfp = fopen(TESTPATH, "r");
+    assert(testfp != NULL);
+    fclose(testfp);
+
+    testfd = open(TESTPATH, O_RDONLY);
+    assert(testfd != -1);
+    close(testfd);
+
+    assert(access(TESTPATH, X_OK) == 0);
+
+    assert(stat(TESTPATH, &testsb) != -1);
+
+    test_spawn();
+    test_execv();
+
+    /* If all goes well, this is never reached because test_execv() replaces
+     * the current process.
+     */
+    return 0;
+}