Previously an `unsafe` block created by the compiler (like those in the
formatting macros) would be "ignored" if surrounded by `unsafe`, that
is, the internal unsafety would be being legitimised by the external
block:
unsafe { println!("...") } =(expansion)=> unsafe { ... unsafe { ... } }
And the code in the inner block would be using the outer block, making
it considered used (and the inner one considered unused).
This patch forces the compiler to create a new unsafe context for
compiler generated blocks, so that their internal unsafety doesn't
escape to external blocks.
Fixes#12418.
Function parameters that are to be passed by value but don't fit into a
single register are currently passed by creating a copy on the stack and
passing a pointer to that copy to the callee. Since the copy is made
just for the function call, there are no aliases.
For example, this sometimes allows LLVM to eliminate unnecessary calls
to drop glue. Given
````rust
struct Foo {
a: int,
b: Option<~str>,
}
extern {
fn eat(eat: Option<~str>);
}
pub fn foo(v: Foo) {
match v {
Foo { a: _, b } => unsafe { eat(b) }
}
}
````
LLVM currently can't eliminate the drop call for the string, because it
only sees a _pointer_ to Foo, for which it has to expect an alias. So we
get:
````llvm
; Function Attrs: uwtable
define void @_ZN3foo20h9f32c90ae7201edbxaa4v0.0E(%struct.Foo* nocapture) unnamed_addr #0 {
"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit":
%1 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 1, i32 0
%2 = load { i64, i64, [0 x i8] }** %1, align 8
store { i64, i64, [0 x i8] }* null, { i64, i64, [0 x i8] }** %1, align 8
%3 = ptrtoint { i64, i64, [0 x i8] }* %2 to i64
%.fca.0.insert = insertvalue { i64 } undef, i64 %3, 0
tail call void @eat({ i64 } %.fca.0.insert)
%4 = load { i64, i64, [0 x i8] }** %1, align 8
%5 = icmp eq { i64, i64, [0 x i8] }* %4, null
br i1 %5, label %_ZN3Foo9glue_drop17hf611996539d3036fE.exit, label %"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i"
"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i": ; preds = %"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit"
%6 = bitcast { i64, i64, [0 x i8] }* %4 to i8*
tail call void @free(i8* %6) #1
br label %_ZN3Foo9glue_drop17hf611996539d3036fE.exit
_ZN3Foo9glue_drop17hf611996539d3036fE.exit: ; preds = %"_ZN34std..option..Option$LT$$UP$str$GT$9glue_drop17hc39b3015f3b9c69dE.exit", %"_ZN8_$UP$str9glue_drop17h15dbdbe2b8897a98E.exit.i.i"
ret void
}
````
But with the `noalias` attribute, it can safely optimize that to:
````llvm
define void @_ZN3foo20hd28431f929f0d6c4xaa4v0.0E(%struct.Foo* noalias nocapture) unnamed_addr #0 {
_ZN3Foo9glue_drop17he9afbc09d4e9c851E.exit:
%1 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 1, i32 0
%2 = load { i64, i64, [0 x i8] }** %1, align 8
store { i64, i64, [0 x i8] }* null, { i64, i64, [0 x i8] }** %1, align 8
%3 = ptrtoint { i64, i64, [0 x i8] }* %2 to i64
%.fca.0.insert = insertvalue { i64 } undef, i64 %3, 0
tail call void @eat({ i64 } %.fca.0.insert)
ret void
}
````
The first setp for #9880 is to add a new `crate` keyword. This PR does exactly that. I took a chance to refactor `parse_item_foreign_mod` and I broke it down into 2 separate methods to isolate each feature.
The next step will be to push a new stage0 snapshot and then get rid of all `extern mod` around the code.
This patch replaces all `crate` usage with `krate` before introducing the
new keyword. This ensures that after introducing the keyword, there
won't be any compilation errors.
krate might not be the most expressive substitution for crate but it's a
very close abbreviation for it. `module` was already used in several
places already.
Error messages cleaned in librustc/middle
Error messages cleaned in libsyntax
Error messages cleaned in libsyntax more agressively
Error messages cleaned in librustc more aggressively
Fixed affected tests
Fixed other failing tests
Last failing tests fixed
The lexer and json were using `transmute(-1): char` as a sentinel value for EOF, which is invalid since `char` is strictly a unicode codepoint.
Fixing this allows for range asserts on chars since they always lie between 0 and 0x10FFFF.
