libredirect: Add a small test

This is just a sanity check on whether the library correctly wraps the
syscalls and it's using the "true" executable for posix_spawn() and
execv().

The installCheckPhase is not executed if we are cross-compiling, so this
shouldn't break cross-compilation.

One thing I'm not actually sure is whether ${coreutils}/bin/true is
universally available on all the platforms, nor whether all the
functions we use in the test are available, but we can still fix that
after we've found out about that.

Signed-off-by: aszlig <aszlig@nix.build>

pkgs/build-support/libredirect/default.nix

@@ -1,21 +1,39 @@
-{ 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
+  '';
 
   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;
+
+  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.unix;
     description = "An LD_PRELOAD library to intercept and rewrite the paths in glibc calls";

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;
+}