diff --git a/classpath/java-io.cpp b/classpath/java-io.cpp
index 6fa22bf359..9bcfa88afd 100644
--- a/classpath/java-io.cpp
+++ b/classpath/java-io.cpp
@@ -314,7 +314,7 @@ Java_java_io_File_toCanonicalPath(JNIEnv* /*e*/, jclass, jstring path)
 }
 
 extern "C" JNIEXPORT jstring JNICALL
-Java_java_io_File_toAbsolutePath(JNIEnv* e, jclass, jstring path)
+Java_java_io_File_toAbsolutePath(JNIEnv* e UNUSED, jclass, jstring path)
 {
 #ifdef PLATFORM_WINDOWS
   // todo
diff --git a/classpath/java-lang.cpp b/classpath/java-lang.cpp
index 8b78a2ec4e..a46b5a93e5 100644
--- a/classpath/java-lang.cpp
+++ b/classpath/java-lang.cpp
@@ -413,8 +413,8 @@ Java_java_lang_Runtime_exec(JNIEnv* e, jclass,
     execvp(argv[0], argv);
     
     // Error if here
-    char c = errno;
-    ssize_t rv UNUSED = write(msg[1], &c, 1);
+    int val = errno;
+    ssize_t rv UNUSED = write(msg[1], &val, sizeof(val));
     exit(127);
   } break;
     
@@ -427,12 +427,13 @@ Java_java_lang_Runtime_exec(JNIEnv* e, jclass,
     safeClose(err[1]);
     safeClose(msg[1]);
       
-    char c;
-    int r = read(msg[0], &c, 1);
+    int val;
+    int r = read(msg[0], &val, sizeof(val));
     if(r == -1) {
       throwNewErrno(e, "java/io/IOException");
       return;
     } else if(r) {
+      errno = val;
       throwNewErrno(e, "java/io/IOException");
       return;
     }
diff --git a/classpath/java/lang/Runtime.java b/classpath/java/lang/Runtime.java
index 30dc0b6612..a24f850bf3 100644
--- a/classpath/java/lang/Runtime.java
+++ b/classpath/java/lang/Runtime.java
@@ -103,7 +103,8 @@ public class Runtime {
 
     if (exception[0] != null) {
       if (exception[0] instanceof IOException) {
-        throw new IOException(exception[0]);
+        String message = "Failed to run \"" + command[0] + "\": " + exception[0].getMessage();
+        throw new IOException(message);
       } else {
         throw new RuntimeException(exception[0]);
       }
diff --git a/makefile b/makefile
index 852cb6a816..a3a6519c2b 100755
--- a/makefile
+++ b/makefile
@@ -240,7 +240,7 @@ endif
 ifeq ($(arch),arm)
 	asm = arm
 	pointer-size = 4
-	ifneq ($(platform),darwin)
+	ifneq ($(build-platform),darwin)
 		cflags += -marm -Wno-psabi
 	endif
 
@@ -262,10 +262,17 @@ ifeq ($(arch),arm)
 	endif
 endif
 
+
 ifeq ($(platform),linux)
 	cflags += -DTARGET_PLATFORM_LINUX
 endif
 
+ifeq ($(build-platform),darwin)
+	build-cflags = $(common-cflags) -fPIC -fvisibility=hidden -I$(src)
+	cflags += -I/System/Library/Frameworks/JavaVM.framework/Headers/
+	build-lflags += -framework CoreFoundation
+endif
+
 ifeq ($(platform),darwin)
 	cflags += -DTARGET_PLATFORM_DARWIN
 
@@ -284,10 +291,6 @@ ifeq ($(platform),darwin)
 		sysroot = /opt/mac/SDKs/MacOSX${OSX_SDK_SYSROOT}.sdk
 		cflags = -I$(sysroot)/System/Library/Frameworks/JavaVM.framework/Versions/1.5.0/Headers/ \
 			$(common-cflags) -fPIC -fvisibility=hidden -I$(src)
-	else
-		build-cflags = $(common-cflags) -fPIC -fvisibility=hidden -I$(src)
-		cflags += -I/System/Library/Frameworks/JavaVM.framework/Headers/
-		build-lflags += -framework CoreFoundation
 	endif
 
 	version-script-flag =
@@ -565,6 +568,9 @@ else
 		-DAVIAN_CLASSPATH=\"[classpathJar]\"
 endif
 
+cflags += $(extra-cflags)
+lflags += $(extra-lflags)
+
 driver-source = $(src)/main.cpp
 driver-object = $(build)/main.o
 driver-dynamic-objects = \