Avoid more `Symbol`-to-string operations
These commits avoid various `Symbol`-to-string conversions, by doing more operations directly on `Symbol`s. This requires adding a few more static `Symbol`s to the binary.
r? @petrochenkov
Keep last redundant linker flag, not first
When a library (L1) is passed to the linker multiple times, this is sometimes purposeful: there might be several other libraries in the linker command (L2 and L3) that all depend on L1. You'd end up with a (simplified) linker command that looks like:
```
-l2 -l1 -l3 -l1
```
With the previous behavior, when rustc encountered a redundant library, it would keep the first instance, and remove the later ones, resulting in:
```
-l2 -l1 -l3
```
This can cause a linker error, because on some platforms (e.g. Linux), the linker will only include symbols from L1 that are needed *at the point it's referenced in the command line*. So if L3 depends on additional symbols from L1, which aren't needed by L2, the linker won't know to include them, and you'll end up with "undefined symbols" errors.
A better behavior is to keep the *last* instance of the library:
```
-l2 -l3 -l1
```
This ensures that all "downstream" libraries have been included in the linker command before the "upstream" library is referenced.
Fixes rust-lang#47989
When a library (L1) is passed to the linker multiple times, this is
sometimes purposeful: there might be several other libraries in the
linker command (L2 and L3) that all depend on L1. You'd end up with a
(simplified) linker command that looks like:
-l2 -l1 -l3 -l1
With the previous behavior, when rustc encountered a redundant library,
it would keep the first instance, and remove the later ones, resulting
in:
-l2 -l1 -l3
This can cause a linker error, because on some platforms (e.g. Linux),
the linker will only include symbols from L1 that are needed *at the
point it's referenced in the command line*. So if L3 depends on
additional symbols from L1, which aren't needed by L2, the linker won't
know to include them, and you'll end up with "undefined symbols" errors.
A better behavior is to keep the *last* instance of the library:
-l2 -l3 -l1
This ensures that all "downstream" libraries have been included in the
linker command before the "upstream" library is referenced.
Fixes rust-lang#47989
This commit stabilizes the `#[wasm_import_module]` attribute as
`#[link(wasm_import_module = "...")]`. Tracked by #52090 this new directive in
the `#[link]` attribute is used to configured the module name that the imports
are listed with. The WebAssembly specification indicates two utf-8 names are
associated with all imported items, one for the module the item comes from and
one for the item itself. The item itself is configurable in Rust via its
identifier or `#[link_name = "..."]`, but the module name was previously not
configurable and defaulted to `"env"`. This commit ensures that this is also
configurable.
Closes#52090
Mazdak Farrokhzad
Vadim Petrochenkov
Mark Rousskov
Camille GILLOT
Guillaume Gomez
Nicholas Nethercote
Shotaro Yamada
Charles Lew
varkor
bors
Samy Kacimi
ljedrz
Jeremy Stucki
Eduard-Mihai Burtescu
Esteban Küber
Taiki Endo
AB1908
Douglas Creager
John Kåre Alsaker
Oliver Scherer
kennytm
Donato Sciarra
Matthias Krüger
Alex Crichton
csmoe
Irina Popa