From d5233ee85ce13cba3dd03e4c0c938cee193b9b19 Mon Sep 17 00:00:00 2001 From: Jakub Konka Date: Thu, 25 Aug 2022 12:38:56 +0200 Subject: add ability to pass force undefined symbols to the linker This commit enables `-u ` for ELF and `-include:` for COFF linkers for use internally. This means we do not expose these flags to the users just yet, however, we make use of them internally whenever required. One such use case is forcing inclusion of `_tls_index` when linking for Windows with mingw and LTO and dead code stripping enabled. This ensures we add `_tls_index` to the symbol resolver as an undefined symbol and force the linker to include an atom that provides it marking it a dead-code-stripping root - meaning it will not be garbage collected by the linker no matter what. --- src/Compilation.zig | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'src/Compilation.zig') diff --git a/src/Compilation.zig b/src/Compilation.zig index 03d7962ccc..353a2f1ca3 100644 --- a/src/Compilation.zig +++ b/src/Compilation.zig @@ -1165,9 +1165,6 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation { break :blk false; } else if (options.c_source_files.len == 0) { break :blk false; - } else if (options.target.os.tag == .windows and link_libcpp) { - // https://github.com/ziglang/zig/issues/8531 - break :blk false; } else if (options.target.cpu.arch.isRISCV()) { // Clang and LLVM currently don't support RISC-V target-abi for LTO. // Compiling with LTO may fail or produce undesired results. @@ -1793,6 +1790,7 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation { .headerpad_size = options.headerpad_size, .headerpad_max_install_names = options.headerpad_max_install_names, .dead_strip_dylibs = options.dead_strip_dylibs, + .force_undefined_symbols = .{}, }); errdefer bin_file.destroy(); comp.* = .{ @@ -1943,6 +1941,10 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation { for (mingw.always_link_libs) |name| { try comp.bin_file.options.system_libs.put(comp.gpa, name, .{}); } + + // LLD might drop some symbols as unused during LTO and GCing, therefore, + // we force mark them for resolution here. + try comp.bin_file.options.force_undefined_symbols.put(comp.gpa, "_tls_index", {}); } // Generate Windows import libs. if (target.os.tag == .windows) { -- cgit v1.2.3