"lld-link: undefined symbol: alloca/_chkstk" -- when trying to link with a llvm-mingw pre-built static library

korke · September 1, 2024, 6:30pm

so according this: GitHub - mstorsjo/llvm-mingw: An LLVM/Clang/LLD based mingw-w64 toolchain

Libtool based projects fail to link with llvm-mingw if the project contains C++. (This often manifests with undefined symbols like ___chkstk_ms, __alloca or ___divdi3.) For such targets, libtool tries to detect which libraries to link by invoking the compiler with $CC -v and picking up the libraries that are linked by default, and then invoking the linker driver with -nostdlib and specifying the default libraries manually. In doing so, libtool fails to detect when clang is using compiler_rt instead of libgcc, because clang refers to it as an absolute path to a static library, instead of specifying a library path with -L and linking the library with -l. Clang is reluctant to changing this behaviour. A bug has been filed with libtool, but no fix has been committed, and as libtool files are shipped with the projects that use them (bundled within the configure script), one has to update the configure script in each project to avoid the issue. This can either be done by installing libtool, patching it and running autoreconf -fi in the project, or by manually applying the fix on the shipped configure script. A patched version of libtool is shipped in MSYS2 at least.

the pre-built static library was configured to link with some other compiler_rt version and it’s mismatching with the zig’s compiler_rt?

these linking errors… it’s so hard to track down the root cause…

Edit:
Some observations:

github.com

ziglang/zig/blob/28383d4d985cd04c897f6b6a63bd2107d8e2a8e9/lib/compiler_rt/stack_probe.zig#L262


      
          pub fn __chkstk() callconv(.Naked) void {
              @setRuntimeSafety(false);
              if (arch == .thumb or arch == .aarch64) {
                  @call(.always_inline, win_probe_stack_only, .{});
              } else switch (arch) {
                  .x86 => @call(.always_inline, win_probe_stack_adjust_sp, .{}),
                  .x86_64 => @call(.always_inline, win_probe_stack_only, .{}),
                  else => unreachable,
              }
          }
          pub fn ___chkstk() callconv(.Naked) void {
              @setRuntimeSafety(false);
              @call(.always_inline, win_probe_stack_adjust_sp, .{});
          }
          pub fn __chkstk_ms() callconv(.Naked) void {
              @setRuntimeSafety(false);
              @call(.always_inline, win_probe_stack_only, .{});
          }
          pub fn ___chkstk_ms() callconv(.Naked) void {
              @setRuntimeSafety(false);
              @call(.always_inline, win_probe_stack_only, .{});

is not exported?

github.com

ziglang/zig/blob/28383d4d985cd04c897f6b6a63bd2107d8e2a8e9/lib/compiler_rt/stack_probe.zig#L16


      
          const is_test = builtin.is_test;
          
          const linkage: std.builtin.GlobalLinkage = if (builtin.is_test) .internal else .weak;
          const strong_linkage: std.builtin.GlobalLinkage = if (builtin.is_test) .internal else .strong;
          pub const panic = @import("common.zig").panic;
          
          comptime {
              if (builtin.os.tag == .windows) {
                  // Default stack-probe functions emitted by LLVM
                  if (builtin.target.isMinGW()) {
                      @export(&_chkstk, .{ .name = "_alloca", .linkage = linkage });
                      @export(&___chkstk_ms, .{ .name = "___chkstk_ms", .linkage = linkage });
          
                      if (arch == .thumb or arch == .aarch64) {
                          @export(&__chkstk, .{ .name = "__chkstk", .linkage = linkage });
                      }
                  } else if (!builtin.link_libc) {
                      // This symbols are otherwise exported by MSVCRT.lib
                      @export(&_chkstk, .{ .name = "_chkstk", .linkage = linkage });
                      @export(&__chkstk, .{ .name = "__chkstk", .linkage = linkage });
                  }

___chkstk was first introduced: Implement stack probes for x86/x86_64 · ziglang/zig@be7cacf · GitHub
but got removed in this pr, couldn’t find any specific comments on them:
compiler_rt: compile each unit separately for improved archiving · ziglang/zig@80790be · GitHub

dimdin · September 1, 2024, 7:21pm

This article can help: An improved chkstk function on Windows
Take your time to read it, it explains what is happening and it is really funny

"lld-link: undefined symbol: __alloca/___chkstk" -- when trying to link with a llvm-mingw pre-built static library

"lld-link: undefined symbol: alloca/_chkstk" -- when trying to link with a llvm-mingw pre-built static library