src/librustc_back/dynamic_lib.rs

   1 // Copyright 2013-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Dynamic library facilities.
  12 //!
  13 //! A simple wrapper over the platform's dynamic library facilities
  14
  15 use std::env;
  16 use std::ffi::{CString, OsString};
  17 use std::path::{Path, PathBuf};
  18
  19 pub struct DynamicLibrary {
  20     handle: *mut u8
  21 }
  22
  23 impl Drop for DynamicLibrary {
  24     fn drop(&mut self) {
  25         unsafe {
  26             dl::close(self.handle)
  27         }
  28     }
  29 }
  30
  31 impl DynamicLibrary {
  32     /// Lazily open a dynamic library. When passed None it gives a
  33     /// handle to the calling process
  34     pub fn open(filename: Option<&Path>) -> Result<DynamicLibrary, String> {
  35         let maybe_library = dl::open(filename.map(|path| path.as_os_str()));
  36
  37         // The dynamic library must not be constructed if there is
  38         // an error opening the library so the destructor does not
  39         // run.
  40         match maybe_library {
  41             Err(err) => Err(err),
  42             Ok(handle) => Ok(DynamicLibrary { handle: handle })
  43         }
  44     }
  45
  46     /// Prepends a path to this process's search path for dynamic libraries
  47     pub fn prepend_search_path(path: &Path) {
  48         let mut search_path = DynamicLibrary::search_path();
  49         search_path.insert(0, path.to_path_buf());
  50         env::set_var(DynamicLibrary::envvar(), &DynamicLibrary::create_path(&search_path));
  51     }
  52
  53     /// From a slice of paths, create a new vector which is suitable to be an
  54     /// environment variable for this platforms dylib search path.
  55     pub fn create_path(path: &[PathBuf]) -> OsString {
  56         let mut newvar = OsString::new();
  57         for (i, path) in path.iter().enumerate() {
  58             if i > 0 { newvar.push(DynamicLibrary::separator()); }
  59             newvar.push(path);
  60         }
  61         return newvar;
  62     }
  63
  64     /// Returns the environment variable for this process's dynamic library
  65     /// search path
  66     pub fn envvar() -> &'static str {
  67         if cfg!(windows) {
  68             "PATH"
  69         } else if cfg!(target_os = "macos") {
  70             "DYLD_LIBRARY_PATH"
  71         } else {
  72             "LD_LIBRARY_PATH"
  73         }
  74     }
  75
  76     fn separator() -> &'static str {
  77         if cfg!(windows) { ";" } else { ":" }
  78     }
  79
  80     /// Returns the current search path for dynamic libraries being used by this
  81     /// process
  82     pub fn search_path() -> Vec<PathBuf> {
  83         match env::var_os(DynamicLibrary::envvar()) {
  84             Some(var) => env::split_paths(&var).collect(),
  85             None => Vec::new(),
  86         }
  87     }
  88
  89     /// Accesses the value at the symbol of the dynamic library.
  90     pub unsafe fn symbol<T>(&self, symbol: &str) -> Result<*mut T, String> {
  91         // This function should have a lifetime constraint of 'a on
  92         // T but that feature is still unimplemented
  93
  94         let raw_string = CString::new(symbol).unwrap();
  95         let maybe_symbol_value = dl::symbol(self.handle, raw_string.as_ptr());
  96
  97         // The value must not be constructed if there is an error so
  98         // the destructor does not run.
  99         match maybe_symbol_value {
 100             Err(err) => Err(err),
 101             Ok(symbol_value) => Ok(symbol_value as *mut T)
 102         }
 103     }
 104 }
 105
 106 #[cfg(test)]
 107 mod tests {
 108     use super::*;
 109     use libc;
 110     use std::mem;
 111
 112     #[test]
 113     fn test_loading_cosine() {
 114         if cfg!(windows) {
 115             return
 116         }
 117
 118         // The math library does not need to be loaded since it is already
 119         // statically linked in
 120         let libm = match DynamicLibrary::open(None) {
 121             Err(error) => panic!("Could not load self as module: {}", error),
 122             Ok(libm) => libm
 123         };
 124
 125         let cosine: extern fn(libc::c_double) -> libc::c_double = unsafe {
 126             match libm.symbol("cos") {
 127                 Err(error) => panic!("Could not load function cos: {}", error),
 128                 Ok(cosine) => mem::transmute::<*mut u8, _>(cosine)
 129             }
 130         };
 131
 132         let argument = 0.0;
 133         let expected_result = 1.0;
 134         let result = cosine(argument);
 135         if result != expected_result {
 136             panic!("cos({}) != {} but equaled {} instead", argument,
 137                    expected_result, result)
 138         }
 139     }
 140
 141     #[test]
 142     fn test_errors_do_not_crash() {
 143         use std::path::Path;
 144
 145         if !cfg!(unix) {
 146             return
 147         }
 148
 149         // Open /dev/null as a library to get an error, and make sure
 150         // that only causes an error, and not a crash.
 151         let path = Path::new("/dev/null");
 152         match DynamicLibrary::open(Some(&path)) {
 153             Err(_) => {}
 154             Ok(_) => panic!("Successfully opened the empty library.")
 155         }
 156     }
 157 }
 158
 159 #[cfg(unix)]
 160 mod dl {
 161     use libc;
 162     use std::ffi::{CStr, OsStr, CString};
 163     use std::os::unix::prelude::*;
 164     use std::ptr;
 165     use std::str;
 166
 167     pub fn open(filename: Option<&OsStr>) -> Result<*mut u8, String> {
 168         check_for_errors_in(|| {
 169             unsafe {
 170                 match filename {
 171                     Some(filename) => open_external(filename),
 172                     None => open_internal(),
 173                 }
 174             }
 175         })
 176     }
 177
 178     const LAZY: libc::c_int = 1;
 179
 180     unsafe fn open_external(filename: &OsStr) -> *mut u8 {
 181         let s = CString::new(filename.as_bytes()).unwrap();
 182         libc::dlopen(s.as_ptr(), LAZY) as *mut u8
 183     }
 184
 185     unsafe fn open_internal() -> *mut u8 {
 186         libc::dlopen(ptr::null(), LAZY) as *mut u8
 187     }
 188
 189     pub fn check_for_errors_in<T, F>(f: F) -> Result<T, String> where
 190         F: FnOnce() -> T,
 191     {
 192         use std::sync::StaticMutex;
 193         static LOCK: StaticMutex = StaticMutex::new();
 194         unsafe {
 195             // dlerror isn't thread safe, so we need to lock around this entire
 196             // sequence
 197             let _guard = LOCK.lock();
 198             let _old_error = libc::dlerror();
 199
 200             let result = f();
 201
 202             let last_error = libc::dlerror() as *const _;
 203             let ret = if ptr::null() == last_error {
 204                 Ok(result)
 205             } else {
 206                 let s = CStr::from_ptr(last_error).to_bytes();
 207                 Err(str::from_utf8(s).unwrap().to_owned())
 208             };
 209
 210             ret
 211         }
 212     }
 213
 214     pub unsafe fn symbol(handle: *mut u8,
 215                          symbol: *const libc::c_char)
 216                          -> Result<*mut u8, String> {
 217         check_for_errors_in(|| {
 218             libc::dlsym(handle as *mut libc::c_void, symbol) as *mut u8
 219         })
 220     }
 221     pub unsafe fn close(handle: *mut u8) {
 222         libc::dlclose(handle as *mut libc::c_void); ()
 223     }
 224 }
 225
 226 #[cfg(windows)]
 227 mod dl {
 228     use std::ffi::OsStr;
 229     use std::io;
 230     use std::os::windows::prelude::*;
 231     use std::ptr;
 232
 233     use libc::{c_uint, c_void, c_char};
 234
 235     type DWORD = u32;
 236     type HMODULE = *mut u8;
 237     type BOOL = i32;
 238     type LPCWSTR = *const u16;
 239     type LPCSTR = *const i8;
 240
 241     extern "system" {
 242         fn SetThreadErrorMode(dwNewMode: DWORD,
 243                               lpOldMode: *mut DWORD) -> c_uint;
 244         fn LoadLibraryW(name: LPCWSTR) -> HMODULE;
 245         fn GetModuleHandleExW(dwFlags: DWORD,
 246                               name: LPCWSTR,
 247                               handle: *mut HMODULE) -> BOOL;
 248         fn GetProcAddress(handle: HMODULE,
 249                           name: LPCSTR) -> *mut c_void;
 250         fn FreeLibrary(handle: HMODULE) -> BOOL;
 251     }
 252
 253     pub fn open(filename: Option<&OsStr>) -> Result<*mut u8, String> {
 254         // disable "dll load failed" error dialog.
 255         let prev_error_mode = unsafe {
 256             // SEM_FAILCRITICALERRORS 0x01
 257             let new_error_mode = 1;
 258             let mut prev_error_mode = 0;
 259             let result = SetThreadErrorMode(new_error_mode,
 260                                             &mut prev_error_mode);
 261             if result == 0 {
 262                 return Err(io::Error::last_os_error().to_string())
 263             }
 264             prev_error_mode
 265         };
 266
 267         let result = match filename {
 268             Some(filename) => {
 269                 let filename_str: Vec<_> =
 270                     filename.encode_wide().chain(Some(0)).collect();
 271                 let result = unsafe {
 272                     LoadLibraryW(filename_str.as_ptr())
 273                 };
 274                 ptr_result(result)
 275             }
 276             None => {
 277                 let mut handle = ptr::null_mut();
 278                 let succeeded = unsafe {
 279                     GetModuleHandleExW(0 as DWORD, ptr::null(), &mut handle)
 280                 };
 281                 if succeeded == 0 {
 282                     Err(io::Error::last_os_error().to_string())
 283                 } else {
 284                     Ok(handle as *mut u8)
 285                 }
 286             }
 287         };
 288
 289         unsafe {
 290             SetThreadErrorMode(prev_error_mode, ptr::null_mut());
 291         }
 292
 293         result
 294     }
 295
 296     pub unsafe fn symbol(handle: *mut u8,
 297                          symbol: *const c_char)
 298                          -> Result<*mut u8, String> {
 299         let ptr = GetProcAddress(handle as HMODULE, symbol) as *mut u8;
 300         ptr_result(ptr)
 301     }
 302
 303     pub unsafe fn close(handle: *mut u8) {
 304         FreeLibrary(handle as HMODULE);
 305     }
 306
 307     fn ptr_result<T>(ptr: *mut T) -> Result<*mut T, String> {
 308         if ptr.is_null() {
 309             Err(io::Error::last_os_error().to_string())
 310         } else {
 311             Ok(ptr)
 312         }
 313     }
 314 }