std: Fix Windows XP compatibility

This commit enables executables linked against the standard library to run on
Windows XP. There are two main components of this commit:

* APIs not available on XP are shimmed to have a fallback implementation and use
  runtime detection to determine if they are available.
* Mutexes on Windows were reimplemented to use critical sections on XP where
  rwlocks are not available.

The APIs which are not available on XP are:

* SetFileInformationByHandle - this is just used by `File::truncate` and that
  function just returns an error now.
* SetThreadStackGuarantee - this is used by the stack overflow support on
  windows, but if this isn't available then it's just ignored (it seems
  non-critical).
* All condition variable APIs are missing - the shims added for these apis
  simply always panic for now. We may eventually provide a fallback
  implementation, but for now the standard library does not rely on condition
  variables for normal use.
* RWLocks, like condition variables, are missing entirely. The same story for
  condition variables is taken here. These APIs are all now panicking stubs as
  the standard library doesn't rely on RWLocks for normal use.

Currently, as an optimization, we use SRWLOCKs for the standard `sync::Mutex`
implementation on Windows, which is indeed required for normal operation of the
standard library. To allow the standard library to run on XP, this commit
reimplements mutexes on Windows to use SRWLOCK instances *if available* and
otherwise a CriticalSection is used (with some checking for recursive
locking).

With all these changes put together, a 32-bit MSVC-built executable can run on
Windows XP and print "hello world"

Closes #12842
Closes #19992
Closes #24776

1 files changed, 12 insertions, 7 deletions

diff --git a/src/libstd/sys/windows/stack_overflow.rs b/src/libstd/sys/windows/stack_overflow.rs
index 79b7de4f341..cf827848db5 100644
--- a/src/libstd/sys/windows/stack_overflow.rs
+++ b/src/libstd/sys/windows/stack_overflow.rs
@@ -8,12 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use rt::util::report_overflow;
 use core::prelude::*;
-use ptr;
-use mem;
+
+use libc::types::os::arch::extra::{LPVOID, DWORD, LONG};
 use libc;
-use libc::types::os::arch::extra::{LPVOID, DWORD, LONG, BOOL};
+use mem;
+use ptr;
+use rt::util::report_overflow;
+use sys::c;
 use sys_common::stack;
 
 pub struct Handler {
@@ -69,8 +71,12 @@ pub unsafe fn cleanup() {
 }
 
 pub unsafe fn make_handler() -> Handler {
-    if SetThreadStackGuarantee(&mut 0x5000) == 0 {
-        panic!("failed to reserve stack space for exception handling");
+    // This API isn't available on XP, so don't panic in that case and just pray
+    // it works out ok.
+    if c::SetThreadStackGuarantee(&mut 0x5000) == 0 {
+        if libc::GetLastError() as u32 != libc::ERROR_CALL_NOT_IMPLEMENTED as u32 {
+            panic!("failed to reserve stack space for exception handling");
+        }
     }
 
     Handler { _data: 0 as *mut libc::c_void }
@@ -103,5 +109,4 @@ extern "system" {
     fn AddVectoredExceptionHandler(FirstHandler: ULONG,
                                    VectoredHandler: PVECTORED_EXCEPTION_HANDLER)
                                   -> LPVOID;
-    fn SetThreadStackGuarantee(StackSizeInBytes: *mut ULONG) -> BOOL;
 }