rust/tests/run-coverage/issue-85461.rs

// Regression test for #85461: MSVC sometimes fail to link with dead code and #[inline(always)]
// aux-build:inline_always_with_dead_code.rs
extern crate inline_always_with_dead_code;

use inline_always_with_dead_code::{bar, baz};

fn main() {
    bar::call_me();
    baz::call_me();
}
code-cov: generate dead functions with private/default linkage As discovered in #85461, the MSVC linker treats weak symbols slightly differently than unix-y linkers do. This causes link.exe to fail with LNK1227 "conflicting weak extern definition" where as other targets are able to link successfully. This changes the dead functions from being generated as weak/hidden to private/default which, as the LLVM reference says: > Global values with “private” linkage are only directly accessible by objects in the current module. In particular, linking code into a module with a private global value may cause the private to be renamed as necessary to avoid collisions. Because the symbol is private to the module, all references can be updated. This doesn’t show up in any symbol table in the object file. This fixes the conflicting weak symbols but doesn't address the reason why we have conflicting symbols for these dead functions. The test cases added in this commit contain a minimal repro of the fundamental issue which is that the logic used to decide what dead code functions should be codegen'd in the current CGU doesn't take into account that functions can be duplicated across multiple CGUs (for instance, in the case of `#[inline(always)]` functions). Fixing that is likely to be a more complex change (see https://github.com/rust-lang/rust/issues/85461#issuecomment-985005805). Fixes #85461 2021-12-02 15:16:34 -06:00			`// Regression test for #85461: MSVC sometimes fail to link with dead code and #[inline(always)]`
Migrate the remaining `run-make/coverage-reports` tests over to `run-coverage` To make it easier to verify that the output snapshots have been migrated faithfully, this change adds some temporary helper code that lets us avoid having to completely re-bless the existing snapshots. A later change in this PR will then re-bless the tests and remove the temporary helper code. 2023-06-12 03:07:04 -05:00			`// aux-build:inline_always_with_dead_code.rs`
code-cov: generate dead functions with private/default linkage As discovered in #85461, the MSVC linker treats weak symbols slightly differently than unix-y linkers do. This causes link.exe to fail with LNK1227 "conflicting weak extern definition" where as other targets are able to link successfully. This changes the dead functions from being generated as weak/hidden to private/default which, as the LLVM reference says: > Global values with “private” linkage are only directly accessible by objects in the current module. In particular, linking code into a module with a private global value may cause the private to be renamed as necessary to avoid collisions. Because the symbol is private to the module, all references can be updated. This doesn’t show up in any symbol table in the object file. This fixes the conflicting weak symbols but doesn't address the reason why we have conflicting symbols for these dead functions. The test cases added in this commit contain a minimal repro of the fundamental issue which is that the logic used to decide what dead code functions should be codegen'd in the current CGU doesn't take into account that functions can be duplicated across multiple CGUs (for instance, in the case of `#[inline(always)]` functions). Fixing that is likely to be a more complex change (see https://github.com/rust-lang/rust/issues/85461#issuecomment-985005805). Fixes #85461 2021-12-02 15:16:34 -06:00			`extern crate inline_always_with_dead_code;`

			`use inline_always_with_dead_code::{bar, baz};`

			`fn main() {`
			`bar::call_me();`
			`baz::call_me();`
			`}`