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Handle link_name attribute #4031

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Handle link_name attribute #4031

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92 changes: 59 additions & 33 deletions gcc/rust/backend/rust-compile-base.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@
#include "rust-compile-implitem.h"
#include "rust-attribute-values.h"
#include "rust-immutable-name-resolution-context.h"
#include "rust-ggc.h"

#include "fold-const.h"
#include "stringpool.h"
Expand All @@ -46,11 +47,59 @@
namespace Rust {
namespace Compile {

bool inline should_mangle_item (const tree fndecl)
tl::optional<GGC::Ident> inline get_unmangled_name (
const std::string &function_name, const AST::AttrVec &attrs)
{
return lookup_attribute (Values::Attributes::NO_MANGLE,
DECL_ATTRIBUTES (fndecl))
== NULL_TREE;
tl::optional<GGC::Ident> set_name;
bool has_no_mangle = false;

// TODO: unused attribute warning on duplicates
for (auto &attr : attrs)
{
auto name = attr.get_path ().as_string ();
if (name == Values::Attributes::NO_MANGLE)
{
has_no_mangle = true;

if (attr.has_attr_input ())
{
rust_error_at (
attr.get_locus (),
"attribute %<no_mangle%> does not accept any arguments");
}
}
else if (name == Values::Attributes::LINK_NAME)
{
AST::AttrInput *input;
AST::LiteralExpr *literal;

if (!attr.has_attr_input ())
goto err_link_name;

input = &attr.get_attr_input ();

if (input->get_attr_input_type ()
!= AST::AttrInput::AttrInputType::LITERAL)
goto err_link_name;
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@P-E-P P-E-P Aug 4, 2025 •
edited
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Not a fan of this goto. You could have split the code in multiple functions and I don't want newcomers to grep the codebase, find this goto and sprinkle some everywhere nor be confused about it.

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good catch yeah avoid goto's please


literal
= &static_cast<AST::AttrInputLiteral &> (*input).get_literal ();

if (literal->get_lit_type () != AST::Literal::LitType::STRING
&& literal->get_lit_type () != AST::Literal::LitType::RAW_STRING)
err_link_name:
rust_error_at (attr.get_locus (),
"malformed %<link_name%> attribute input");
else
// TODO: special handling for STRING/RAW_STRING?
// later attributes do override earlier ones
set_name = literal->as_string ();
}
}

if (!set_name.has_value () && has_no_mangle)
set_name = function_name;
return set_name;
}

void
Expand Down Expand Up @@ -84,8 +133,6 @@ HIRCompileBase::setup_fndecl (tree fndecl, bool is_main_entry_point,
bool is_cold = attr.get_path ().as_string () == Values::Attributes::COLD;
bool is_link_section
= attr.get_path ().as_string () == Values::Attributes::LINK_SECTION;
bool no_mangle
= attr.get_path ().as_string () == Values::Attributes::NO_MANGLE;
bool is_deprecated
= attr.get_path ().as_string () == Values::Attributes::DEPRECATED;
bool is_proc_macro
Expand Down Expand Up @@ -116,10 +163,6 @@ HIRCompileBase::setup_fndecl (tree fndecl, bool is_main_entry_point,
{
handle_deprecated_attribute_on_fndecl (fndecl, attr);
}
else if (no_mangle)
{
handle_no_mangle_attribute_on_fndecl (fndecl, attr);
}
else if (is_proc_macro)
{
handle_bang_proc_macro_attribute_on_fndecl (fndecl, attr);
Expand Down Expand Up @@ -272,22 +315,6 @@ HIRCompileBase::handle_link_section_attribute_on_fndecl (
set_decl_section_name (fndecl, msg_str.c_str ());
}

void
HIRCompileBase::handle_no_mangle_attribute_on_fndecl (
tree fndecl, const AST::Attribute &attr)
{
if (attr.has_attr_input ())
{
rust_error_at (attr.get_locus (),
"attribute %<no_mangle%> does not accept any arguments");
return;
}

DECL_ATTRIBUTES (fndecl)
= tree_cons (get_identifier (Values::Attributes::NO_MANGLE), NULL_TREE,
DECL_ATTRIBUTES (fndecl));
}

void
HIRCompileBase::handle_deprecated_attribute_on_fndecl (
tree fndecl, const AST::Attribute &attr)
Expand Down Expand Up @@ -705,7 +732,6 @@ HIRCompileBase::compile_function (
/* So that 'MAIN_NAME_P' works. */
main_identifier_node = get_identifier (ir_symbol_name.c_str ());
}
std::string asm_name = fn_name;

unsigned int flags = 0;
tree fndecl = Backend::function (compiled_fn_type, ir_symbol_name,
Expand All @@ -716,12 +742,12 @@ HIRCompileBase::compile_function (
setup_abi_options (fndecl, get_abi (outer_attrs, qualifiers));

// conditionally mangle the function name
bool should_mangle = should_mangle_item (fndecl);
if (!is_main_fn && should_mangle)
asm_name = ctx->mangle_item (fntype, canonical_path);
SET_DECL_ASSEMBLER_NAME (fndecl,
get_identifier_with_length (asm_name.data (),
asm_name.length ()));
auto unmangled
= is_main_fn ? "main" : get_unmangled_name (fn_name, outer_attrs);
GGC::Ident asm_name
= unmangled ? *unmangled : ctx->mangle_item (fntype, canonical_path);

SET_DECL_ASSEMBLER_NAME (fndecl, asm_name.as_tree ());

// insert into the context
ctx->insert_function_decl (fntype, fndecl);
Expand Down
3 changes: 0 additions & 3 deletions gcc/rust/backend/rust-compile-base.h
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Original file line number Diff line number Diff line change
Expand Up @@ -149,9 +149,6 @@ class HIRCompileBase
handle_deprecated_attribute_on_fndecl (tree fndecl,
const AST::Attribute &attr);

static void handle_no_mangle_attribute_on_fndecl (tree fndecl,
const AST::Attribute &attr);

static void setup_abi_options (tree fndecl, ABI abi);

static tree indirect_expression (tree expr, location_t locus);
Expand Down
1 change: 1 addition & 0 deletions gcc/rust/util/rust-attribute-values.h
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Expand Up @@ -37,6 +37,7 @@ class Attributes
static constexpr auto &MUST_USE = "must_use";
static constexpr auto &LANG = "lang";
static constexpr auto &LINK_SECTION = "link_section";
static constexpr auto &LINK_NAME = "link_name";
static constexpr auto &NO_MANGLE = "no_mangle";
static constexpr auto &REPR = "repr";
static constexpr auto &RUSTC_BUILTIN_MACRO = "rustc_builtin_macro";
Expand Down
1 change: 1 addition & 0 deletions gcc/rust/util/rust-attributes.cc
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Expand Up @@ -54,6 +54,7 @@ static const BuiltinAttrDefinition __definitions[]
{Attrs::MUST_USE, STATIC_ANALYSIS},
{Attrs::LANG, HIR_LOWERING},
{Attrs::LINK_SECTION, CODE_GENERATION},
{Attrs::LINK_NAME, CODE_GENERATION},
{Attrs::NO_MANGLE, CODE_GENERATION},
{Attrs::REPR, CODE_GENERATION},
{Attrs::RUSTC_BUILTIN_MACRO, EXPANSION},
Expand Down
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