Remove fixed_stack_segment

doc/tutorial-ffi.md

@@ -19,10 +19,9 @@ extern {
     fn snappy_max_compressed_length(source_length: size_t) -> size_t;
 }
 
-#[fixed_stack_segment]
 fn main() {
     let x = unsafe { snappy_max_compressed_length(100) };
-    println(fmt!("max compressed length of a 100 byte buffer: %?", x));
+    println!("max compressed length of a 100 byte buffer: {}", x);
 }
 ~~~~
 
@@ -36,11 +35,6 @@ interfaces that aren't thread-safe, and almost any function that takes a pointer
 valid for all possible inputs since the pointer could be dangling, and raw pointers fall outside of
 Rust's safe memory model.
 
-Finally, the `#[fixed_stack_segment]` annotation that appears on
-`main()` instructs the Rust compiler that when `main()` executes, it
-should request a "very large" stack segment.  More details on
-stack management can be found in the following sections.
-
 When declaring the argument types to a foreign function, the Rust compiler will not check if the
 declaration is correct, so specifying it correctly is part of keeping the binding correct at
 runtime.
@@ -81,8 +75,6 @@ length is number of elements currently contained, and the capacity is the total
 the allocated memory. The length is less than or equal to the capacity.
 
 ~~~~ {.xfail-test}
-#[fixed_stack_segment]
-#[inline(never)]
 pub fn validate_compressed_buffer(src: &[u8]) -> bool {
     unsafe {
         snappy_validate_compressed_buffer(vec::raw::to_ptr(src), src.len() as size_t) == 0
@@ -94,36 +86,6 @@ The `validate_compressed_buffer` wrapper above makes use of an `unsafe` block, b
 guarantee that calling it is safe for all inputs by leaving off `unsafe` from the function
 signature.
 
-The `validate_compressed_buffer` wrapper is also annotated with two
-attributes `#[fixed_stack_segment]` and `#[inline(never)]`. The
-purpose of these attributes is to guarantee that there will be
-sufficient stack for the C function to execute. This is necessary
-because Rust, unlike C, does not assume that the stack is allocated in
-one continuous chunk. Instead, we rely on a *segmented stack* scheme,
-in which the stack grows and shrinks as necessary.  C code, however,
-expects one large stack, and so callers of C functions must request a
-large stack segment to ensure that the C routine will not run off the
-end of the stack.
-
-The compiler includes a lint mode that will report an error if you
-call a C function without a `#[fixed_stack_segment]` attribute. More
-details on the lint mode are given in a later section.
-
-You may be wondering why we include a `#[inline(never)]` directive.
-This directive informs the compiler never to inline this function.
-While not strictly necessary, it is usually a good idea to use an
-`#[inline(never)]` directive in concert with `#[fixed_stack_segment]`.
-The reason is that if a fn annotated with `fixed_stack_segment` is
-inlined, then its caller also inherits the `fixed_stack_segment`
-annotation. This means that rather than requesting a large stack
-segment only for the duration of the call into C, the large stack
-segment would be used for the entire duration of the caller. This is
-not necessarily *bad* -- it can for example be more efficient,
-particularly if `validate_compressed_buffer()` is called multiple
-times in a row -- but it does work against the purpose of the
-segmented stack scheme, which is to keep stacks small and thus
-conserve address space.
-
 The `snappy_compress` and `snappy_uncompress` functions are more complex, since a buffer has to be
 allocated to hold the output too.
 
@@ -134,8 +96,6 @@ the true length after compression for setting the length.
 
 ~~~~ {.xfail-test}
 pub fn compress(src: &[u8]) -> ~[u8] {
-    #[fixed_stack_segment]; #[inline(never)];
-
     unsafe {
         let srclen = src.len() as size_t;
         let psrc = vec::raw::to_ptr(src);
@@ -156,8 +116,6 @@ format and `snappy_uncompressed_length` will retrieve the exact buffer size requ
 
 ~~~~ {.xfail-test}
 pub fn uncompress(src: &[u8]) -> Option<~[u8]> {
-    #[fixed_stack_segment]; #[inline(never)];
-
     unsafe {
         let srclen = src.len() as size_t;
         let psrc = vec::raw::to_ptr(src);
@@ -181,98 +139,28 @@ pub fn uncompress(src: &[u8]) -> Option<~[u8]> {
 For reference, the examples used here are also available as an [library on
 GitHub](https://github.com/thestinger/rust-snappy).
 
-# Automatic wrappers
-
-Sometimes writing Rust wrappers can be quite tedious.  For example, if
-function does not take any pointer arguments, often there is no need
-for translating types. In such cases, it is usually still a good idea
-to have a Rust wrapper so as to manage the segmented stacks, but you
-can take advantage of the (standard) `externfn!` macro to remove some
-of the tedium.
-
-In the initial section, we showed an extern block that added a call
-to a specific snappy API:
-
-~~~~ {.xfail-test}
-use std::libc::size_t;
-
-#[link_args = "-lsnappy"]
-extern {
-    fn snappy_max_compressed_length(source_length: size_t) -> size_t;
-}
-
-#[fixed_stack_segment]
-fn main() {
-    let x = unsafe { snappy_max_compressed_length(100) };
-    println(fmt!("max compressed length of a 100 byte buffer: %?", x));
-}
-~~~~
-
-To avoid the need to create a wrapper fn for `snappy_max_compressed_length()`,
-and also to avoid the need to think about `#[fixed_stack_segment]`, we
-could simply use the `externfn!` macro instead, as shown here:
-
-~~~~ {.xfail-test}
-use std::libc::size_t;
-
-externfn!(#[link_args = "-lsnappy"]
-          fn snappy_max_compressed_length(source_length: size_t) -> size_t)
-
-fn main() {
-    let x = unsafe { snappy_max_compressed_length(100) };
-    println(fmt!("max compressed length of a 100 byte buffer: %?", x));
-}
-~~~~
-
-As you can see from the example, `externfn!` replaces the extern block
-entirely. After macro expansion, it will create something like this:
-
-~~~~ {.xfail-test}
-use std::libc::size_t;
-
-// Automatically generated by
-//   externfn!(#[link_args = "-lsnappy"]
-//             fn snappy_max_compressed_length(source_length: size_t) -> size_t)
-unsafe fn snappy_max_compressed_length(source_length: size_t) -> size_t {
-    #[fixed_stack_segment]; #[inline(never)];
-    return snappy_max_compressed_length(source_length);
-
-    #[link_args = "-lsnappy"]
-    extern {
-        fn snappy_max_compressed_length(source_length: size_t) -> size_t;
-    }
-}
-
-fn main() {
-    let x = unsafe { snappy_max_compressed_length(100) };
-    println(fmt!("max compressed length of a 100 byte buffer: %?", x));
-}
-~~~~
-
-# Segmented stacks and the linter
-
-By default, whenever you invoke a non-Rust fn, the `cstack` lint will
-check that one of the following conditions holds:
-
-1. The call occurs inside of a fn that has been annotated with
-   `#[fixed_stack_segment]`;
-2. The call occurs inside of an `extern fn`;
-3. The call occurs within a stack closure created by some other
-   safe fn.
-
-All of these conditions ensure that you are running on a large stack
-segment. However, they are sometimes too strict. If your application
-will be making many calls into C, it is often beneficial to promote
-the `#[fixed_stack_segment]` attribute higher up the call chain.  For
-example, the Rust compiler actually labels main itself as requiring a
-`#[fixed_stack_segment]`. In such cases, the linter is just an
-annoyance, because all C calls that occur from within the Rust
-compiler are made on a large stack. Another situation where this
-frequently occurs is on a 64-bit architecture, where large stacks are
-the default. In cases, you can disable the linter by including a
-`#[allow(cstack)]` directive somewhere, which permits violations of
-the "cstack" rules given above (you can also use `#[warn(cstack)]` to
-convert the errors into warnings, if you prefer).
+# Stack management
+
+Rust tasks by default run on a "large stack". This is actually implemented as a
+reserving a large segment of the address space and then lazily mapping in pages
+as they are needed. When calling an external C function, the code is invoked on
+the same stack as the rust stack. This means that there is no extra
+stack-switching mechanism in place because it is assumed that the large stack
+for the rust task is plenty for the C function to have.
+
+A planned future improvement (net yet implemented at the time of this writing)
+is to have a guard page at the end of every rust stack. No rust function will
+hit this guard page (due to rust's usage of LLVM's __morestack). The intention
+for this unmapped page is to prevent infinite recursion in C from overflowing
+onto other rust stacks. If the guard page is hit, then the process will be
+terminated with a message saying that the guard page was hit.
+
+For normal external function usage, this all means that there shouldn't be any
+need for any extra effort on a user's perspective. The C stack naturally
+interleaves with the rust stack, and it's "large enough" for both to
+interoperate. If, however, it is determined that a larger stack is necessary,
+there are appropriate functions in the task spawning API to control the size of
+the stack of the task which is spawned.
 
 # Destructors
 
@@ -296,9 +184,6 @@ pub struct Unique<T> {
 
 impl<T: Send> Unique<T> {
     pub fn new(value: T) -> Unique<T> {
-        #[fixed_stack_segment];
-        #[inline(never)];
-
         unsafe {
             let ptr = malloc(std::mem::size_of::<T>() as size_t) as *mut T;
             assert!(!ptr::is_null(ptr));
@@ -322,9 +207,6 @@ impl<T: Send> Unique<T> {
 #[unsafe_destructor]
 impl<T: Send> Drop for Unique<T> {
     fn drop(&mut self) {
-        #[fixed_stack_segment];
-        #[inline(never)];
-
         unsafe {
             let x = intrinsics::init(); // dummy value to swap in
             // moving the object out is needed to call the destructor
@@ -384,8 +266,8 @@ extern {
 }
 
 fn main() {
-    println(fmt!("You have readline version %d installed.",
-                 rl_readline_version as int));
+    println!("You have readline version {} installed.",
+             rl_readline_version as int);
 }
 ~~~
 

src/libextra/c_vec.rs

@@ -162,7 +162,6 @@ mod tests {
     }
 
     impl Runnable for LibcFree {
-        #[fixed_stack_segment]
         fn run(~self) {
             unsafe {
                 libc::free(self.mem)
@@ -171,9 +170,6 @@ mod tests {
     }
 
     fn malloc(n: size_t) -> CVec<u8> {
-        #[fixed_stack_segment];
-        #[inline(never)];
-
         unsafe {
             let mem = libc::malloc(n);
 

src/libextra/flate.rs

@@ -47,8 +47,6 @@ static TINFL_FLAG_PARSE_ZLIB_HEADER : c_int = 0x1; // parse zlib header and adle
 static TDEFL_WRITE_ZLIB_HEADER : c_int = 0x01000; // write zlib header and adler32 checksum
 
 fn deflate_bytes_internal(bytes: &[u8], flags: c_int) -> ~[u8] {
-    #[fixed_stack_segment]; #[inline(never)];
-
     do bytes.as_imm_buf |b, len| {
         unsafe {
             let mut outsz : size_t = 0;
@@ -75,8 +73,6 @@ pub fn deflate_bytes_zlib(bytes: &[u8]) -> ~[u8] {
 }
 
 fn inflate_bytes_internal(bytes: &[u8], flags: c_int) -> ~[u8] {
-    #[fixed_stack_segment]; #[inline(never)];
-
     do bytes.as_imm_buf |b, len| {
         unsafe {
             let mut outsz : size_t = 0;

src/libextra/lib.rs

@@ -38,6 +38,8 @@ Rust extras are part of the standard Rust distribution.
 
 #[deny(non_camel_case_types)];
 #[deny(missing_doc)];
+#[allow(unrecognized_lint)]; // NOTE: remove after the next snapshot
+#[allow(cstack)]; // NOTE: remove after the next snapshot.
 
 use std::str::{StrSlice, OwnedStr};
 

src/libextra/test.rs

@@ -220,8 +220,6 @@ fn optgroups() -> ~[getopts::groups::OptGroup] {
 }
 
 fn usage(binary: &str, helpstr: &str) {
-    #[fixed_stack_segment]; #[inline(never)];
-
     let message = format!("Usage: {} [OPTIONS] [FILTER]", binary);
     println(groups::usage(message, optgroups()));
     println("");

src/libextra/time.rs

@@ -63,8 +63,6 @@ impl Ord for Timespec {
  * nanoseconds since 1970-01-01T00:00:00Z.
  */
 pub fn get_time() -> Timespec {
-    #[fixed_stack_segment]; #[inline(never)];
-
     unsafe {
         let mut sec = 0i64;
         let mut nsec = 0i32;
@@ -79,8 +77,6 @@ pub fn get_time() -> Timespec {
  * in nanoseconds since an unspecified epoch.
  */
 pub fn precise_time_ns() -> u64 {
-    #[fixed_stack_segment]; #[inline(never)];
-
     unsafe {
         let mut ns = 0u64;
         rustrt::precise_time_ns(&mut ns);
@@ -98,8 +94,6 @@ pub fn precise_time_s() -> f64 {
 }
 
 pub fn tzset() {
-    #[fixed_stack_segment]; #[inline(never)];
-
     unsafe {
         rustrt::rust_tzset();
     }
@@ -143,8 +137,6 @@ pub fn empty_tm() -> Tm {
 
 /// Returns the specified time in UTC
 pub fn at_utc(clock: Timespec) -> Tm {
-    #[fixed_stack_segment]; #[inline(never)];
-
     unsafe {
         let Timespec { sec, nsec } = clock;
         let mut tm = empty_tm();
@@ -160,8 +152,6 @@ pub fn now_utc() -> Tm {
 
 /// Returns the specified time in the local timezone
 pub fn at(clock: Timespec) -> Tm {
-    #[fixed_stack_segment]; #[inline(never)];
-
     unsafe {
         let Timespec { sec, nsec } = clock;
         let mut tm = empty_tm();
@@ -179,8 +169,6 @@ pub fn now() -> Tm {
 impl Tm {
     /// Convert time to the seconds from January 1, 1970
     pub fn to_timespec(&self) -> Timespec {
-        #[fixed_stack_segment]; #[inline(never)];
-
         unsafe {
             let sec = match self.tm_gmtoff {
                 0_i32 => rustrt::rust_timegm(self),
@@ -969,7 +957,6 @@ mod tests {
     use std::libc;
 
     #[cfg(windows)]
-    #[fixed_stack_segment]
     fn set_time_zone() {
         // Windows crt doesn't see any environment variable set by
         // `SetEnvironmentVariable`, which `os::setenv` internally uses.

src/librustc/driver/driver.rs

@@ -278,9 +278,6 @@ pub fn phase_3_run_analysis_passes(sess: Session,
     time(time_passes, "loop checking", (), |_|
          middle::check_loop::check_crate(ty_cx, crate));
 
-    time(time_passes, "stack checking", (), |_|
-         middle::stack_check::stack_check_crate(ty_cx, crate));
-
     let middle::moves::MoveMaps {moves_map, moved_variables_set,
                                  capture_map} =
         time(time_passes, "compute moves", (), |_|
@@ -428,7 +425,6 @@ pub fn stop_after_phase_5(sess: Session) -> bool {
     return false;
 }
 
-#[fixed_stack_segment]
 pub fn compile_input(sess: Session, cfg: ast::CrateConfig, input: &input,
                      outdir: &Option<Path>, output: &Option<Path>) {
     // We need nested scopes here, because the intermediate results can keep
@@ -703,12 +699,7 @@ pub fn build_session_options(binary: @str,
     }
 
     if debugging_opts & session::debug_llvm != 0 {
-        set_llvm_debug();
-
-        fn set_llvm_debug() {
-            #[fixed_stack_segment]; #[inline(never)];
-            unsafe { llvm::LLVMSetDebug(1); }
-        }
+        unsafe { llvm::LLVMSetDebug(1); }
     }
 
     let output_type =