src/libstd/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 #![unstable(feature = "dynamic_lib",
  16             reason = "API has not been scrutinized and is highly likely to \
  17                       either disappear or change")]
  18 #![allow(missing_docs)]
  19
  20 use prelude::v1::*;
  21
  22 use env;
  23 use ffi::{CString, OsString};
  24 use mem;
  25 use path::{Path, PathBuf};
  26
  27 pub struct DynamicLibrary {
  28     handle: *mut u8
  29 }
  30
  31 impl Drop for DynamicLibrary {
  32     fn drop(&mut self) {
  33         match dl::check_for_errors_in(|| {
  34             unsafe {
  35                 dl::close(self.handle)
  36             }
  37         }) {
  38             Ok(()) => {},
  39             Err(str) => panic!("{}", str)
  40         }
  41     }
  42 }
  43
  44 impl DynamicLibrary {
  45     /// Lazily open a dynamic library. When passed None it gives a
  46     /// handle to the calling process
  47     pub fn open(filename: Option<&Path>) -> Result<DynamicLibrary, String> {
  48         let maybe_library = dl::open(filename.map(|path| path.as_os_str()));
  49
  50         // The dynamic library must not be constructed if there is
  51         // an error opening the library so the destructor does not
  52         // run.
  53         match maybe_library {
  54             Err(err) => Err(err),
  55             Ok(handle) => Ok(DynamicLibrary { handle: handle })
  56         }
  57     }
  58
  59     /// Prepends a path to this process's search path for dynamic libraries
  60     pub fn prepend_search_path(path: &Path) {
  61         let mut search_path = DynamicLibrary::search_path();
  62         search_path.insert(0, path.to_path_buf());
  63         env::set_var(DynamicLibrary::envvar(), &DynamicLibrary::create_path(&search_path));
  64     }
  65
  66     /// From a slice of paths, create a new vector which is suitable to be an
  67     /// environment variable for this platforms dylib search path.
  68     pub fn create_path(path: &[PathBuf]) -> OsString {
  69         let mut newvar = OsString::new();
  70         for (i, path) in path.iter().enumerate() {
  71             if i > 0 { newvar.push(DynamicLibrary::separator()); }
  72             newvar.push(path);
  73         }
  74         return newvar;
  75     }
  76
  77     /// Returns the environment variable for this process's dynamic library
  78     /// search path
  79     pub fn envvar() -> &'static str {
  80         if cfg!(windows) {
  81             "PATH"
  82         } else if cfg!(target_os = "macos") {
  83             "DYLD_LIBRARY_PATH"
  84         } else {
  85             "LD_LIBRARY_PATH"
  86         }
  87     }
  88
  89     fn separator() -> &'static str {
  90         if cfg!(windows) { ";" } else { ":" }
  91     }
  92
  93     /// Returns the current search path for dynamic libraries being used by this
  94     /// process
  95     pub fn search_path() -> Vec<PathBuf> {
  96         match env::var_os(DynamicLibrary::envvar()) {
  97             Some(var) => env::split_paths(&var).collect(),
  98             None => Vec::new(),
  99         }
 100     }
 101
 102     /// Accesses the value at the symbol of the dynamic library.
 103     pub unsafe fn symbol<T>(&self, symbol: &str) -> Result<*mut T, String> {
 104         // This function should have a lifetime constraint of 'a on
 105         // T but that feature is still unimplemented
 106
 107         let raw_string = CString::new(symbol).unwrap();
 108         let maybe_symbol_value = dl::check_for_errors_in(|| {
 109             dl::symbol(self.handle, raw_string.as_ptr())
 110         });
 111
 112         // The value must not be constructed if there is an error so
 113         // the destructor does not run.
 114         match maybe_symbol_value {
 115             Err(err) => Err(err),
 116             Ok(symbol_value) => Ok(mem::transmute(symbol_value))
 117         }
 118     }
 119 }
 120
 121 #[cfg(all(test, not(target_os = "ios")))]
 122 mod tests {
 123     use super::*;
 124     use prelude::v1::*;
 125     use libc;
 126     use mem;
 127     use path::Path;
 128
 129     #[test]
 130     #[cfg_attr(any(windows,
 131                    target_os = "android",  // FIXME #10379
 132                    target_env = "musl"), ignore)]
 133     fn test_loading_cosine() {
 134         // The math library does not need to be loaded since it is already
 135         // statically linked in
 136         let libm = match DynamicLibrary::open(None) {
 137             Err(error) => panic!("Could not load self as module: {}", error),
 138             Ok(libm) => libm
 139         };
 140
 141         let cosine: extern fn(libc::c_double) -> libc::c_double = unsafe {
 142             match libm.symbol("cos") {
 143                 Err(error) => panic!("Could not load function cos: {}", error),
 144                 Ok(cosine) => mem::transmute::<*mut u8, _>(cosine)
 145             }
 146         };
 147
 148         let argument = 0.0;
 149         let expected_result = 1.0;
 150         let result = cosine(argument);
 151         if result != expected_result {
 152             panic!("cos({}) != {} but equaled {} instead", argument,
 153                    expected_result, result)
 154         }
 155     }
 156
 157     #[test]
 158     #[cfg(any(target_os = "linux",
 159               target_os = "macos",
 160               target_os = "freebsd",
 161               target_os = "dragonfly",
 162               target_os = "bitrig",
 163               target_os = "openbsd"))]
 164     fn test_errors_do_not_crash() {
 165         // Open /dev/null as a library to get an error, and make sure
 166         // that only causes an error, and not a crash.
 167         let path = Path::new("/dev/null");
 168         match DynamicLibrary::open(Some(&path)) {
 169             Err(_) => {}
 170             Ok(_) => panic!("Successfully opened the empty library.")
 171         }
 172     }
 173 }
 174
 175 #[cfg(any(target_os = "linux",
 176           target_os = "android",
 177           target_os = "macos",
 178           target_os = "ios",
 179           target_os = "freebsd",
 180           target_os = "dragonfly",
 181           target_os = "bitrig",
 182           target_os = "openbsd"))]
 183 mod dl {
 184     use prelude::v1::*;
 185
 186     use ffi::{CStr, OsStr};
 187     use str;
 188     use libc;
 189     use ptr;
 190
 191     pub fn open(filename: Option<&OsStr>) -> Result<*mut u8, String> {
 192         check_for_errors_in(|| {
 193             unsafe {
 194                 match filename {
 195                     Some(filename) => open_external(filename),
 196                     None => open_internal(),
 197                 }
 198             }
 199         })
 200     }
 201
 202     const LAZY: libc::c_int = 1;
 203
 204     unsafe fn open_external(filename: &OsStr) -> *mut u8 {
 205         let s = filename.to_cstring().unwrap();
 206         dlopen(s.as_ptr(), LAZY) as *mut u8
 207     }
 208
 209     unsafe fn open_internal() -> *mut u8 {
 210         dlopen(ptr::null(), LAZY) as *mut u8
 211     }
 212
 213     pub fn check_for_errors_in<T, F>(f: F) -> Result<T, String> where
 214         F: FnOnce() -> T,
 215     {
 216         use sync::StaticMutex;
 217         static LOCK: StaticMutex = StaticMutex::new();
 218         unsafe {
 219             // dlerror isn't thread safe, so we need to lock around this entire
 220             // sequence
 221             let _guard = LOCK.lock();
 222             let _old_error = dlerror();
 223
 224             let result = f();
 225
 226             let last_error = dlerror() as *const _;
 227             let ret = if ptr::null() == last_error {
 228                 Ok(result)
 229             } else {
 230                 let s = CStr::from_ptr(last_error).to_bytes();
 231                 Err(str::from_utf8(s).unwrap().to_string())
 232             };
 233
 234             ret
 235         }
 236     }
 237
 238     pub unsafe fn symbol(handle: *mut u8,
 239                          symbol: *const libc::c_char) -> *mut u8 {
 240         dlsym(handle as *mut libc::c_void, symbol) as *mut u8
 241     }
 242     pub unsafe fn close(handle: *mut u8) {
 243         dlclose(handle as *mut libc::c_void); ()
 244     }
 245
 246     extern {
 247         fn dlopen(filename: *const libc::c_char,
 248                   flag: libc::c_int) -> *mut libc::c_void;
 249         fn dlerror() -> *mut libc::c_char;
 250         fn dlsym(handle: *mut libc::c_void,
 251                  symbol: *const libc::c_char) -> *mut libc::c_void;
 252         fn dlclose(handle: *mut libc::c_void) -> libc::c_int;
 253     }
 254 }
 255
 256 #[cfg(target_os = "windows")]
 257 mod dl {
 258     use prelude::v1::*;
 259
 260     use ffi::OsStr;
 261     use libc;
 262     use libc::consts::os::extra::ERROR_CALL_NOT_IMPLEMENTED;
 263     use sys::os;
 264     use os::windows::prelude::*;
 265     use ptr;
 266     use sys::c::compat::kernel32::SetThreadErrorMode;
 267
 268     pub fn open(filename: Option<&OsStr>) -> Result<*mut u8, String> {
 269         // disable "dll load failed" error dialog.
 270         let mut use_thread_mode = true;
 271         let prev_error_mode = unsafe {
 272             // SEM_FAILCRITICALERRORS 0x01
 273             let new_error_mode = 1;
 274             let mut prev_error_mode = 0;
 275             // Windows >= 7 supports thread error mode.
 276             let result = SetThreadErrorMode(new_error_mode, &mut prev_error_mode);
 277             if result == 0 {
 278                 let err = os::errno();
 279                 if err as libc::c_int == ERROR_CALL_NOT_IMPLEMENTED {
 280                     use_thread_mode = false;
 281                     // SetThreadErrorMode not found. use fallback solution:
 282                     // SetErrorMode() Note that SetErrorMode is process-wide so
 283                     // this can cause race condition!  However, since even
 284                     // Windows APIs do not care of such problem (#20650), we
 285                     // just assume SetErrorMode race is not a great deal.
 286                     prev_error_mode = SetErrorMode(new_error_mode);
 287                 }
 288             }
 289             prev_error_mode
 290         };
 291
 292         unsafe {
 293             SetLastError(0);
 294         }
 295
 296         let result = match filename {
 297             Some(filename) => {
 298                 let filename_str: Vec<_> =
 299                     filename.encode_wide().chain(Some(0)).collect();
 300                 let result = unsafe {
 301                     LoadLibraryW(filename_str.as_ptr() as *const libc::c_void)
 302                 };
 303                 // beware: Vec/String may change errno during drop!
 304                 // so we get error here.
 305                 if result == ptr::null_mut() {
 306                     let errno = os::errno();
 307                     Err(os::error_string(errno))
 308                 } else {
 309                     Ok(result as *mut u8)
 310                 }
 311             }
 312             None => {
 313                 let mut handle = ptr::null_mut();
 314                 let succeeded = unsafe {
 315                     GetModuleHandleExW(0 as libc::DWORD, ptr::null(), &mut handle)
 316                 };
 317                 if succeeded == libc::FALSE {
 318                     let errno = os::errno();
 319                     Err(os::error_string(errno))
 320                 } else {
 321                     Ok(handle as *mut u8)
 322                 }
 323             }
 324         };
 325
 326         unsafe {
 327             if use_thread_mode {
 328                 SetThreadErrorMode(prev_error_mode, ptr::null_mut());
 329             } else {
 330                 SetErrorMode(prev_error_mode);
 331             }
 332         }
 333
 334         result
 335     }
 336
 337     pub fn check_for_errors_in<T, F>(f: F) -> Result<T, String> where
 338         F: FnOnce() -> T,
 339     {
 340         unsafe {
 341             SetLastError(0);
 342
 343             let result = f();
 344
 345             let error = os::errno();
 346             if 0 == error {
 347                 Ok(result)
 348             } else {
 349                 Err(format!("Error code {}", error))
 350             }
 351         }
 352     }
 353
 354     pub unsafe fn symbol(handle: *mut u8, symbol: *const libc::c_char) -> *mut u8 {
 355         GetProcAddress(handle as *mut libc::c_void, symbol) as *mut u8
 356     }
 357     pub unsafe fn close(handle: *mut u8) {
 358         FreeLibrary(handle as *mut libc::c_void); ()
 359     }
 360
 361     #[allow(non_snake_case)]
 362     extern "system" {
 363         fn SetLastError(error: libc::size_t);
 364         fn LoadLibraryW(name: *const libc::c_void) -> *mut libc::c_void;
 365         fn GetModuleHandleExW(dwFlags: libc::DWORD, name: *const u16,
 366                               handle: *mut *mut libc::c_void) -> libc::BOOL;
 367         fn GetProcAddress(handle: *mut libc::c_void,
 368                           name: *const libc::c_char) -> *mut libc::c_void;
 369         fn FreeLibrary(handle: *mut libc::c_void);
 370         fn SetErrorMode(uMode: libc::c_uint) -> libc::c_uint;
 371     }
 372 }