Commit 819716b59f941253ae98405bb4b30049aea5f8de | zig

author	Isaac Freund <mail@isaacfreund.com> 2025-01-29 14:11:23+01:00
committer	Isaac Freund <mail@isaacfreund.com> 2025-02-10 23:19:48+01:00
log	819716b59f941253ae98405bb4b30049aea5f8de
tree	0e501e960750e089393647b4bf74a518b18cda61
parent	34644511bb6d83aa6575641ef79e5eefb495e3e1
signature	Commit is signed but in an unrecognized format.

link: fix ambiguous names in linker scripts

Currently zig fails to build while linking the system LLVM/C++ libraries
on my Chimera Linux system due to the fact that libc++.so is a linker
script with the following contents:

INPUT(libc++.so.1 -lc++abi -lunwind)

Prior to this commit, zig would try to convert "ambiguous names" in
linker scripts such as libc++.so.1 in this example into -lfoo style
flags. This fails in this case due to the so version number as zig
checks for exactly the .so suffix.

Furthermore, I do not think that this conversion is semantically correct
since converting libfoo.so to -lfoo could theoretically end up resulting
in libfoo.a getting linked which seems wrong when a different file is
specified in the linker script.

With this patch, this attempted conversion is removed. Instead, zig
always first checks if the exact file/path in the linker script exists
relative to the current working directory.

If the file is classified as a library (including versioned shared
objects such as libfoo.so.1), zig then falls back to checking if
the exact file/path in the linker script exists relative to each
directory in the library search path, selecting the first match or
erroring out if none is found.

This behavior fixes the regression that prevents building zig while
linking the system LLVM/C++ libraries on Chimera Linux.

2 files changed, 87 insertions(+), 53 deletions(-)

src
- link.zig
test
- link
  - elf.zig

src/link.zig+68-45

 @@ -1891,30 +1891,69 @@ pub fn resolveInputs(
     syslib: while (unresolved_inputs.pop()) |unresolved_input| {
         const name_query: UnresolvedInput.NameQuery = switch (unresolved_input) {
             .name_query => |nq| nq,
-            .ambiguous_name => |an| an: {
+            .ambiguous_name => |an| {
-                const lib_name, const link_mode = stripLibPrefixAndSuffix(an.name, target) orelse {
+                // First check the path relative to the current working directory.
-                    try resolvePathInput(gpa, arena, unresolved_inputs, resolved_inputs, &ld_script_bytes, target, .{
+                // If the file is a library and is not found there, check the library search paths as well.
+                // This is consistent with the behavior of GNU ld.
+                if (try resolvePathInput(
+                    gpa,
+                    arena,
+                    unresolved_inputs,
+                    resolved_inputs,
+                    &ld_script_bytes,
+                    target,
+                    .{
                         .path = Path.initCwd(an.name),
                         .query = an.query,
-                    }, color);
-                    continue;
-                };
-                break :an .{
-                    .name = lib_name,
-                    .query = .{
-                        .needed = an.query.needed,
-                        .weak = an.query.weak,
-                        .reexport = an.query.reexport,
-                        .must_link = an.query.must_link,
-                        .hidden = an.query.hidden,
-                        .allow_so_scripts = an.query.allow_so_scripts,
-                        .preferred_mode = link_mode,
-                        .search_strategy = .no_fallback,
                     },
-                };
+                    color,
+                )) |lib_result| {
+                    switch (lib_result) {
+                        .ok => continue :syslib,
+                        .no_match => {
+                            for (lib_directories) |lib_directory| {
+                                switch ((try resolvePathInput(
+                                    gpa,
+                                    arena,
+                                    unresolved_inputs,
+                                    resolved_inputs,
+                                    &ld_script_bytes,
+                                    target,
+                                    .{
+                                        .path = .{
+                                            .root_dir = lib_directory,
+                                            .sub_path = an.name,
+                                        },
+                                        .query = an.query,
+                                    },
+                                    color,
+                                )).?) {
+                                    .ok => continue :syslib,
+                                    .no_match => {},
+                                }
+                            }
+                            fatal("{s}: file listed in linker script not found", .{an.name});
+                        },
+                    }
+                }
+                continue;
             },
             .path_query => |pq| {
-                try resolvePathInput(gpa, arena, unresolved_inputs, resolved_inputs, &ld_script_bytes, target, pq, color);
+                if (try resolvePathInput(
+                    gpa,
+                    arena,
+                    unresolved_inputs,
+                    resolved_inputs,
+                    &ld_script_bytes,
+                    target,
+                    pq,
+                    color,
+                )) |lib_result| {
+                    switch (lib_result) {
+                        .ok => {},
+                        .no_match => fatal("{}: file not found", .{pq.path}),
+                    }
+                }
                 continue;
             },
             .dso_exact => |dso_exact| {
 @@ -2176,10 +2215,10 @@ fn resolvePathInput(
     target: std.Target,
     pq: UnresolvedInput.PathQuery,
     color: std.zig.Color,
-) Allocator.Error!void {
+) Allocator.Error!?ResolveLibInputResult {
-    switch (switch (Compilation.classifyFileExt(pq.path.sub_path)) {
+    switch (Compilation.classifyFileExt(pq.path.sub_path)) {
-        .static_library => try resolvePathInputLib(gpa, arena, unresolved_inputs, resolved_inputs, ld_script_bytes, target, pq, .static, color),
+        .static_library => return try resolvePathInputLib(gpa, arena, unresolved_inputs, resolved_inputs, ld_script_bytes, target, pq, .static, color),
-        .shared_library => try resolvePathInputLib(gpa, arena, unresolved_inputs, resolved_inputs, ld_script_bytes, target, pq, .dynamic, color),
+        .shared_library => return try resolvePathInputLib(gpa, arena, unresolved_inputs, resolved_inputs, ld_script_bytes, target, pq, .dynamic, color),
         .object => {
             var file = pq.path.root_dir.handle.openFile(pq.path.sub_path, .{}) catch |err|
                 fatal("failed to open object {}: {s}", .{ pq.path, @errorName(err) });
 @@ -2190,7 +2229,7 @@ fn resolvePathInput(
                 .must_link = pq.query.must_link,
                 .hidden = pq.query.hidden,
             } });
-            return;
+            return null;
         },
         .res => {
             var file = pq.path.root_dir.handle.openFile(pq.path.sub_path, .{}) catch |err|
 @@ -2200,12 +2239,9 @@ fn resolvePathInput(
                 .path = pq.path,
                 .file = file,
             } });
-            return;
+            return null;
         },
         else => fatal("{}: unrecognized file extension", .{pq.path}),
-    }) {
-        .ok => {},
-        .no_match => fatal("{}: file not found", .{pq.path}),
     }
 }
 @@ -2226,9 +2262,11 @@ fn resolvePathInputLib(
     try resolved_inputs.ensureUnusedCapacity(gpa, 1);
     const test_path: Path = pq.path;
-    // In the case of .so files, they might actually be "linker scripts"
+    // In the case of shared libraries, they might actually be "linker scripts"
     // that contain references to other libraries.
-    if (pq.query.allow_so_scripts and target.ofmt == .elf and mem.endsWith(u8, test_path.sub_path, ".so")) {
+    if (pq.query.allow_so_scripts and target.ofmt == .elf and
+        Compilation.classifyFileExt(test_path.sub_path) == .shared_library)
+    {
         var file = test_path.root_dir.handle.openFile(test_path.sub_path, .{}) catch |err| switch (err) {
             error.FileNotFound => return .no_match,
             else => |e| fatal("unable to search for {s} library '{'}': {s}", .{
 @@ -2354,21 +2392,6 @@ pub fn openDsoInput(diags: *Diags, path: Path, needed: bool, weak: bool, reexpor
     } };
 }
-fn stripLibPrefixAndSuffix(path: []const u8, target: std.Target) ?struct { []const u8, std.builtin.LinkMode } {
-    const prefix = target.libPrefix();
-    const static_suffix = target.staticLibSuffix();
-    const dynamic_suffix = target.dynamicLibSuffix();
-    const basename = fs.path.basename(path);
-    const unlibbed = if (mem.startsWith(u8, basename, prefix)) basename[prefix.len..] else return null;
-    if (mem.endsWith(u8, unlibbed, static_suffix)) return .{
-        unlibbed[0 .. unlibbed.len - static_suffix.len], .static,
-    };
-    if (mem.endsWith(u8, unlibbed, dynamic_suffix)) return .{
-        unlibbed[0 .. unlibbed.len - dynamic_suffix.len], .dynamic,
-    };
-    return null;
-}
 /// Returns true if and only if there is at least one input of type object,
 /// archive, or Windows resource file.
 pub fn anyObjectInputs(inputs: []const Input) bool {

test/link/elf.zig+19-8

 @@ -2123,24 +2123,35 @@ fn testLinkOrder(b: *Build, opts: Options) *Step {
 fn testLdScript(b: *Build, opts: Options) *Step {
     const test_step = addTestStep(b, "ld-script", opts);
-    const dso = addSharedLibrary(b, opts, .{ .name = "bar" });
+    const bar = addSharedLibrary(b, opts, .{ .name = "bar" });
-    addCSourceBytes(dso, "int foo() { return 42; }", &.{});
+    addCSourceBytes(bar, "int bar() { return 42; }", &.{});
+    const baz = addSharedLibrary(b, opts, .{ .name = "baz" });
+    addCSourceBytes(baz, "int baz() { return 42; }", &.{});
     const scripts = WriteFile.create(b);
-    _ = scripts.add("liba.so", "INPUT(libfoo.so)");
+    _ = scripts.add("liba.so", "INPUT(libfoo.so libfoo2.so.1)");
     _ = scripts.add("libfoo.so", "GROUP(AS_NEEDED(-lbar))");
+    // Check finding a versioned .so file that is elsewhere in the library search paths.
+    const scripts2 = WriteFile.create(b);
+    _ = scripts2.add("libfoo2.so.1", "GROUP(AS_NEEDED(-lbaz))");
     const exe = addExecutable(b, opts, .{ .name = "main" });
     addCSourceBytes(exe,
-        \\int foo();
+        \\int bar();
+        \\int baz();
         \\int main() {
-        \\  return foo() - 42;
+        \\  return bar() - baz();
         \\}
     , &.{});
     exe.linkSystemLibrary2("a", .{});
     exe.addLibraryPath(scripts.getDirectory());
-    exe.addLibraryPath(dso.getEmittedBinDirectory());
+    exe.addLibraryPath(scripts2.getDirectory());
-    exe.addRPath(dso.getEmittedBinDirectory());
+    exe.addLibraryPath(bar.getEmittedBinDirectory());
+    exe.addLibraryPath(baz.getEmittedBinDirectory());
+    exe.addRPath(bar.getEmittedBinDirectory());
+    exe.addRPath(baz.getEmittedBinDirectory());
     exe.linkLibC();
     exe.allow_so_scripts = true;
 @@ -2167,7 +2178,7 @@ fn testLdScriptPathError(b: *Build, opts: Options) *Step {
     // TODO: A future enhancement could make this error message also mention
     // the file that references the missing library.
     expectLinkErrors(exe, test_step, .{
-        .stderr_contains = "error: unable to find dynamic system library 'foo' using strategy 'no_fallback'. searched paths:",
+        .stderr_contains = "error: libfoo.so: file listed in linker script not found",
     });
     return test_step;