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Properly set the linkage type on non-local statics

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Fixes issue #18804

Signed-off-by: Gabriel Smith <ga29smith@gmail.com>
This commit is contained in:
Gabriel Smith 2018-07-22 19:30:52 -04:00
parent e8bc064c5e
commit a20262c069
1 changed files with 53 additions and 6 deletions
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59
src/librustc_codegen_llvm/consts.rs
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@ -119,6 +119,8 @@ pub fn get_static(cx: &CodegenCx, def_id: DefId) -> ValueRef {
let ty = instance.ty(cx.tcx);
let sym = cx.tcx.symbol_name(instance).as_str();
debug!("get_static: sym={} instance={:?}", sym, instance);
let g = if let Some(id) = cx.tcx.hir.as_local_node_id(def_id) {
let llty = cx.layout_of(ty).llvm_type(cx);
@ -145,6 +147,8 @@ pub fn get_static(cx: &CodegenCx, def_id: DefId) -> ValueRef {
ref attrs, span, node: hir::ForeignItemKind::Static(..), ..
}) => {
let g = if let Some(linkage) = cx.tcx.codegen_fn_attrs(def_id).linkage {
debug!("get_static: sym={} linkage={:?}", sym, linkage);
// If this is a static with a linkage specified, then we need to handle
// it a little specially. The typesystem prevents things like &T and
// extern "C" fn() from being non-null, so we can't just declare a
@ -188,6 +192,8 @@ pub fn get_static(cx: &CodegenCx, def_id: DefId) -> ValueRef {
item => bug!("get_static: expected static, found {:?}", item)
};
debug!("get_static: sym={} attrs={:?}", sym, attrs);
for attr in attrs {
if attr.check_name("thread_local") {
llvm::set_thread_local_mode(g, cx.tls_model);
@ -197,19 +203,60 @@ pub fn get_static(cx: &CodegenCx, def_id: DefId) -> ValueRef {
g
} else {
// FIXME(nagisa): perhaps the map of externs could be offloaded to llvm somehow?
// FIXME(nagisa): investigate whether it can be changed into define_global
let g = declare::declare_global(cx, &sym, cx.layout_of(ty).llvm_type(cx));
debug!("get_static: sym={} item_attr={:?}", sym, cx.tcx.item_attrs(def_id));
let codegen_fn_attrs = cx.tcx.codegen_fn_attrs(def_id);
let llty = cx.layout_of(ty).llvm_type(cx);
let g = if let Some(linkage) = codegen_fn_attrs.linkage {
debug!("get_static: sym={} linkage={:?}", sym, linkage);
// If this is a static with a linkage specified, then we need to handle
// it a little specially. The typesystem prevents things like &T and
// extern "C" fn() from being non-null, so we can't just declare a
// static and call it a day. Some linkages (like weak) will make it such
// that the static actually has a null value.
let llty2 = match ty.sty {
ty::TyRawPtr(ref mt) => cx.layout_of(mt.ty).llvm_type(cx),
_ => {
bug!("must have type `*const T` or `*mut T`")
}
};
unsafe {
// Declare a symbol `foo` with the desired linkage.
let g1 = declare::declare_global(cx, &sym, llty2);
llvm::LLVMRustSetLinkage(g1, base::linkage_to_llvm(linkage));
// Declare an internal global `extern_with_linkage_foo` which
// is initialized with the address of `foo`. If `foo` is
// discarded during linking (for example, if `foo` has weak
// linkage and there are no definitions), then
// `extern_with_linkage_foo` will instead be initialized to
// zero.
let mut real_name = "_rust_extern_with_linkage_".to_string();
real_name.push_str(&sym);
let g2 = declare::define_global(cx, &real_name, llty).unwrap_or_else(||{
bug!("symbol `{}` is already defined", &sym)
});
llvm::LLVMRustSetLinkage(g2, llvm::Linkage::InternalLinkage);
llvm::LLVMSetInitializer(g2, g1);
g2
}
} else {
// Generate an external declaration.
// FIXME(nagisa): investigate whether it can be changed into define_global
declare::declare_global(cx, &sym, llty)
};
// Thread-local statics in some other crate need to *always* be linked
// against in a thread-local fashion, so we need to be sure to apply the
// thread-local attribute locally if it was present remotely. If we
// don't do this then linker errors can be generated where the linker
// complains that one object files has a thread local version of the
// symbol and another one doesn't.
for attr in cx.tcx.get_attrs(def_id).iter() {
if attr.check_name("thread_local") {
llvm::set_thread_local_mode(g, cx.tls_model);
}
if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
llvm::set_thread_local_mode(g, cx.tls_model);
}
if cx.use_dll_storage_attrs && !cx.tcx.is_foreign_item(def_id) {
// This item is external but not foreign, i.e. it originates from an external Rust
// crate. Since we don't know whether this crate will be linked dynamically or