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fix_libc++_cannot_find_stdmodule #7074

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315ddb0
fix_libc++_cannot_find_stdmodule
Nov 28, 2025
4d1579d
try_two_methods
Nov 29, 2025
5a88ba3
parse_chain_of_symbolic_link
Nov 29, 2025
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58 changes: 47 additions & 11 deletions xmake/rules/c++/modules/clang/support.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -243,25 +243,61 @@ function get_clang_scan_deps(target)
return clang_scan_deps or nil
end

function get_stdmodules(target)
function parse_link_files(filepath)
if not os.islink(filepath) then
return filepath
end
local target = os.readlink(filepath)
if path.is_absolute(target) then
return target
end
return path.join(path.directory(filepath), target)
end

function get_original_file(filepath)
while os.islink(filepath) do
filepath = parse_link_files(filepath)
end
return filepath
end
Comment on lines +246 to +262
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@gemini-code-assist gemini-code-assist bot Nov 30, 2025

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medium

The new functions parse_link_files and get_original_file are only used within this file. It's good practice to declare them as local to limit their scope and avoid polluting the module's global namespace.

local function parse_link_files(filepath)
    if not os.islink(filepath) then
        return filepath
    end
    local target = os.readlink(filepath)
    if path.is_absolute(target) then
        return target
    end
    return path.join(path.directory(filepath), target)
end

local function get_original_file(filepath)
    while os.islink(filepath) do
        filepath = parse_link_files(filepath)
    end
    return filepath
end


function get_stdmodules(target)
local cpplib = get_cpplibrary_name(target)
if cpplib then
if cpplib == "c++" then
-- libc++ module is found by parsing libc++.modules.json
local modules_json_path = _get_std_module_manifest_path(target)
if modules_json_path then
local modules_json = json.decode(io.readfile(modules_json_path))
if modules_json and modules_json.modules and #modules_json.modules > 0 then
local std_module_directory = path.directory(modules_json.modules[1]["source-path"])
if not path.is_absolute(std_module_directory) then
std_module_directory = path.join(path.directory(modules_json_path), std_module_directory)
end
if os.isdir(std_module_directory) then
return {path.normalize(path.join(std_module_directory, "std.cppm")), path.normalize(path.join(std_module_directory, "std.compat.cppm"))}
end
if not modules_json_path then
wprint("libc++.modules.json not found! maybe try to add --sdk=<PATH/TO/LLVM> or install libc++")
return
end
local modules_json = json.decode(io.readfile(modules_json_path))
if not (modules_json and modules_json.modules and #modules_json.modules > 0) then
wprint("libc++.modules.json is invalid! path: %s", path.normalize(modules_json_path))
return
end
local std_module_directory = path.directory(modules_json.modules[1]["source-path"])
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high

The code does not check if modules_json.modules[1]["source-path"] exists before using it. If it's nil, path.directory(nil) will be called, which becomes path.directory("nil") and returns . This would lead to incorrect path resolution. It's safer to check for the existence of "source-path" and print a warning if it's missing.

            local source_path = modules_json.modules[1]["source-path"]
            if not source_path then
                wprint("source-path not found in libc++.modules.json: %s", path.normalize(modules_json_path))
                return
            end
            local std_module_directory = path.directory(source_path)

-- check absolute path first
if path.is_absolute(std_module_directory) then
if os.isdir(std_module_directory) then
return {path.normalize(path.join(std_module_directory, "std.cppm")), path.normalize(path.join(std_module_directory, "std.compat.cppm"))}
else
wprint("std module directory not found: %s which defined in %s", path.normalize(std_module_directory), path.normalize(modules_json_path))
return
end
end
-- otherwise try to resolve relative path
local try_std_module_directory
-- first try the directory relative to libc++.modules.json
try_std_module_directory = path.join(path.directory(modules_json_path), std_module_directory)
if os.isdir(try_std_module_directory) then
return {path.normalize(path.join(try_std_module_directory, "std.cppm")), path.normalize(path.join(try_std_module_directory, "std.compat.cppm"))}
end
-- then try the directory relative to clang bin directory
try_std_module_directory = path.join(path.directory(get_original_file(get_clang_path(target))), std_module_directory)
if os.isdir(try_std_module_directory) then
return {path.normalize(path.join(try_std_module_directory, "std.cppm")), path.normalize(path.join(try_std_module_directory, "std.compat.cppm"))}
end
Comment on lines +297 to +300
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high

get_clang_path(target) can return nil, which would cause get_original_file(nil) to be called. This will likely lead to a runtime error. You should check if get_clang_path returns a valid path before using it.

            local clang_path = get_clang_path(target)
            if clang_path then
                try_std_module_directory = path.join(path.directory(get_original_file(clang_path)), std_module_directory)
                if os.isdir(try_std_module_directory) then
                    return {path.normalize(path.join(try_std_module_directory, "std.cppm")), path.normalize(path.join(try_std_module_directory, "std.compat.cppm"))}
                end
            end

elseif cpplib == "stdc++" then
-- dont be greedy and don't enable stdc++ std module support for llvm < 19
local clang_version = get_clang_version(target)
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