From 42c0494499b3ee271bafa68bbfe5eb5176442c4d Mon Sep 17 00:00:00 2001 From: David Lattimore Date: Fri, 11 Oct 2024 07:58:36 +1100 Subject: [PATCH] Use Default visibility for rustc-generated C symbol declarations Non-default visibilities should only be used for definitions, not declarations, otherwise linking can fail. Co-authored-by: Collin Baker --- compiler/rustc_codegen_llvm/src/declare.rs | 7 +++---- tests/codegen/default-visibility.rs | 16 ++++++++++++++++ 2 files changed, 19 insertions(+), 4 deletions(-) diff --git a/compiler/rustc_codegen_llvm/src/declare.rs b/compiler/rustc_codegen_llvm/src/declare.rs index 7be44dd51b5..33258cb46fa 100644 --- a/compiler/rustc_codegen_llvm/src/declare.rs +++ b/compiler/rustc_codegen_llvm/src/declare.rs @@ -84,10 +84,9 @@ pub(crate) fn declare_cfn( unnamed: llvm::UnnamedAddr, fn_type: &'ll Type, ) -> &'ll Value { - // Declare C ABI functions with the visibility used by C by default. - let visibility = Visibility::from_generic(self.tcx.sess.default_visibility()); - - declare_raw_fn(self, name, llvm::CCallConv, unnamed, visibility, fn_type) + // Visibility should always be default for declarations, otherwise the linker may report an + // error. + declare_raw_fn(self, name, llvm::CCallConv, unnamed, Visibility::Default, fn_type) } /// Declare an entry Function diff --git a/tests/codegen/default-visibility.rs b/tests/codegen/default-visibility.rs index 884d386ec20..88ff9fee254 100644 --- a/tests/codegen/default-visibility.rs +++ b/tests/codegen/default-visibility.rs @@ -31,3 +31,19 @@ // PROTECTED: @{{.*}}default_visibility{{.*}}tested_symbol{{.*}} = protected constant // INTERPOSABLE: @{{.*}}default_visibility{{.*}}tested_symbol{{.*}} = constant // DEFAULT: @{{.*}}default_visibility{{.*}}tested_symbol{{.*}} = constant + +pub fn do_memcmp(left: &[u8], right: &[u8]) -> i32 { + left.cmp(right) as i32 +} + +// CHECK: define {{.*}} @{{.*}}do_memcmp{{.*}} { +// CHECK: } + +// `do_memcmp` should invoke core::intrinsic::compare_bytes which emits a call +// to the C symbol `memcmp` (at least on x86_64-unknown-linux-gnu). This symbol +// should *not* be declared hidden or protected. + +// HIDDEN: declare i32 @memcmp +// PROTECTED: declare i32 @memcmp +// INTERPOSABLE: declare i32 @memcmp +// DEFAULT: declare i32 @memcmp