Improvements for dlfcn

src/header/dlfcn/mod.rs

 //! dlfcn implementation for Redox, following http://pubs.opengroup.org/onlinepubs/7908799/xsh/dlfcn.h.html
 
 use core::{ptr, str};
+use core::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
 
 use c_str::CStr;
 use platform::types::*;
@@ -10,6 +11,11 @@ pub const RTLD_NOW: c_int = 0x0002;
 pub const RTLD_GLOBAL: c_int = 0x0100;
 pub const RTLD_LOCAL: c_int = 0x0000;
 
+static ERROR_NOT_SUPPORTED: &'static CStr = c_str!("dlfcn not supported");
+
+#[thread_local]
+static ERROR: AtomicUsize = ATOMIC_USIZE_INIT;
+
 #[repr(C)]
 pub struct Dl_info {
     dli_fname: *const c_char,
@@ -29,14 +35,32 @@ pub unsafe extern "C" fn dladdr(addr: *mut c_void, info: *mut Dl_info) -> c_int
 
 #[no_mangle]
 pub unsafe extern "C" fn dlopen(filename: *const c_char, flags: c_int) -> *mut c_void {
-    let filename_cstr = CStr::from_ptr(filename);
-    let filename_str = str::from_utf8_unchecked(filename_cstr.to_bytes());
-    eprintln!("dlopen({}, {:#>04X})", filename_str, flags);
-    ptr::null_mut()
+    let filename_opt = if filename.is_null() {
+        None
+    } else {
+        Some(str::from_utf8_unchecked(CStr::from_ptr(filename).to_bytes()))
+    };
+
+    eprintln!("dlopen({:?}, {:#>04x})", filename_opt, flags);
+
+    if let Some(filename) = filename_opt {
+        ERROR.store(ERROR_NOT_SUPPORTED.as_ptr() as usize, Ordering::SeqCst);
+        ptr::null_mut()
+    } else {
+        1 as *mut c_void
+    }
 }
 
 #[no_mangle]
-pub extern "C" fn dlsym(handle: *mut c_void, symbol: *const c_char) -> *mut c_void {
+pub unsafe extern "C" fn dlsym(handle: *mut c_void, symbol: *const c_char) -> *mut c_void {
+    let symbol_opt = if symbol.is_null() {
+        None
+    } else {
+        Some(str::from_utf8_unchecked(CStr::from_ptr(symbol).to_bytes()))
+    };
+
+    eprintln!("dlsym({:p}, {:?})", handle, symbol_opt);
+
     ptr::null_mut()
 }
 
@@ -47,5 +71,5 @@ pub extern "C" fn dlclose(handle: *mut c_void) -> c_int {
 
 #[no_mangle]
 pub extern "C" fn dlerror() -> *mut c_char {
-    ptr::null_mut()
+    ERROR.swap(0, Ordering::SeqCst) as *mut c_char
 }