linker: fail the compilation if there were linker errors

There was no check for linker errors after flushing,
which meant that if the link failed the build would
continue and try to copy the non-existant exe, and
also write the manifest as if it had succeeded.

Also adds parsing of lld output, which is surfaced at the
end of the compilation with the other errors instead
of via stderr

4 files changed, 98 insertions, 15 deletions

diff --git a/src/Compilation.zig b/src/Compilation.zig
index 50afe2c7b6..60064fefd1 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -51,6 +51,7 @@ whole_cache_manifest: ?*Cache.Manifest = null,
 whole_cache_manifest_mutex: std.Thread.Mutex = .{},
 
 link_error_flags: link.File.ErrorFlags = .{},
+lld_errors: std.ArrayListUnmanaged(LldError) = .{},
 
 work_queue: std.fifo.LinearFifo(Job, .Dynamic),
 anon_work_queue: std.fifo.LinearFifo(Job, .Dynamic),
@@ -335,6 +336,21 @@ pub const MiscError = struct {
     }
 };
 
+pub const LldError = struct {
+    /// Allocated with gpa.
+    msg: []const u8,
+    context_lines: []const []const u8 = &.{},
+
+    pub fn deinit(self: *LldError, gpa: Allocator) void {
+        for (self.context_lines) |line| {
+            gpa.free(line);
+        }
+
+        gpa.free(self.context_lines);
+        gpa.free(self.msg);
+    }
+};
+
 /// To support incremental compilation, errors are stored in various places
 /// so that they can be created and destroyed appropriately. This structure
 /// is used to collect all the errors from the various places into one
@@ -498,7 +514,7 @@ pub const AllErrors = struct {
                     }
                     ttyconf.setColor(stderr, .Reset);
                     for (plain.notes) |note| {
-                        try note.renderToWriter(ttyconf, stderr, "error", .Red, indent + 4);
+                        try note.renderToWriter(ttyconf, stderr, "note", .Cyan, indent + 4);
                     }
                 },
             }
@@ -2166,6 +2182,11 @@ pub fn destroy(self: *Compilation) void {
     }
     self.failed_c_objects.deinit(gpa);
 
+    for (self.lld_errors.items) |*lld_error| {
+        lld_error.deinit(gpa);
+    }
+    self.lld_errors.deinit(gpa);
+
     self.clearMiscFailures();
 
     self.cache_parent.manifest_dir.close();
@@ -2465,6 +2486,10 @@ pub fn update(comp: *Compilation) !void {
             try comp.flush(main_progress_node);
         }
 
+        if (comp.totalErrorCount() != 0) {
+            return;
+        }
+
         // Failure here only means an unnecessary cache miss.
         man.writeManifest() catch |err| {
             log.warn("failed to write cache manifest: {s}", .{@errorName(err)});
@@ -2494,7 +2519,7 @@ fn flush(comp: *Compilation, prog_node: *std.Progress.Node) !void {
     // This is needed before reading the error flags.
     comp.bin_file.flush(comp, prog_node) catch |err| switch (err) {
         error.FlushFailure => {}, // error reported through link_error_flags
-        error.LLDReportedFailure => {}, // error reported through log.err
+        error.LLDReportedFailure => {}, // error reported via lockAndParseLldStderr
         else => |e| return e,
     };
     comp.link_error_flags = comp.bin_file.errorFlags();
@@ -2727,7 +2752,7 @@ pub fn makeBinFileWritable(self: *Compilation) !void {
 /// This function is temporally single-threaded.
 pub fn totalErrorCount(self: *Compilation) usize {
     var total: usize = self.failed_c_objects.count() + self.misc_failures.count() +
-        @boolToInt(self.alloc_failure_occurred);
+        @boolToInt(self.alloc_failure_occurred) + self.lld_errors.items.len;
 
     if (self.bin_file.options.module) |module| {
         total += module.failed_exports.count();
@@ -2815,6 +2840,21 @@ pub fn getAllErrorsAlloc(self: *Compilation) !AllErrors {
             });
         }
     }
+    for (self.lld_errors.items) |lld_error| {
+        const notes = try arena_allocator.alloc(AllErrors.Message, lld_error.context_lines.len);
+        for (lld_error.context_lines) |context_line, i| {
+            notes[i] = .{ .plain = .{
+                .msg = try arena_allocator.dupe(u8, context_line),
+            } };
+        }
+
+        try errors.append(.{
+            .plain = .{
+                .msg = try arena_allocator.dupe(u8, lld_error.msg),
+                .notes = notes,
+            },
+        });
+    }
     for (self.misc_failures.values()) |*value| {
         try AllErrors.addPlainWithChildren(&arena, &errors, value.msg, value.children);
     }
@@ -4989,6 +5029,52 @@ pub fn lockAndSetMiscFailure(
     return setMiscFailure(comp, tag, format, args);
 }
 
+fn parseLldStderr(comp: *Compilation, comptime prefix: []const u8, stderr: []const u8) Allocator.Error!void {
+    var context_lines = std.ArrayList([]const u8).init(comp.gpa);
+    defer context_lines.deinit();
+
+    var current_err: ?*LldError = null;
+    var lines = mem.split(u8, stderr, std.cstr.line_sep);
+    while (lines.next()) |line| {
+        if (mem.startsWith(u8, line, prefix ++ ":")) {
+            if (current_err) |err| {
+                err.context_lines = context_lines.toOwnedSlice();
+            }
+
+            var split = std.mem.split(u8, line, "error: ");
+            _ = split.first();
+
+            const duped_msg = try std.fmt.allocPrint(comp.gpa, "{s}: {s}", .{ prefix, split.rest() });
+            errdefer comp.gpa.free(duped_msg);
+
+            current_err = try comp.lld_errors.addOne(comp.gpa);
+            current_err.?.* = .{ .msg = duped_msg };
+        } else if (current_err != null) {
+            const context_prefix = ">>> ";
+            var trimmed = mem.trimRight(u8, line, &std.ascii.whitespace);
+            if (mem.startsWith(u8, trimmed, context_prefix)) {
+                trimmed = trimmed[context_prefix.len..];
+            }
+
+            if (trimmed.len > 0) {
+                const duped_line = try comp.gpa.dupe(u8, trimmed);
+                try context_lines.append(duped_line);
+            }
+        }
+    }
+
+    if (current_err) |err| {
+        err.context_lines = context_lines.toOwnedSlice();
+    }
+}
+
+pub fn lockAndParseLldStderr(comp: *Compilation, comptime prefix: []const u8, stderr: []const u8) void {
+    comp.mutex.lock();
+    defer comp.mutex.unlock();
+
+    comp.parseLldStderr(prefix, stderr) catch comp.setAllocFailure();
+}
+
 pub fn dump_argv(argv: []const []const u8) void {
     for (argv[0 .. argv.len - 1]) |arg| {
         std.debug.print("{s} ", .{arg});
diff --git a/src/link/Coff/lld.zig b/src/link/Coff/lld.zig
index 00e6c4d8d1..ebc2208606 100644
--- a/src/link/Coff/lld.zig
+++ b/src/link/Coff/lld.zig
@@ -175,7 +175,8 @@ pub fn linkWithLLD(self: *Coff, comp: *Compilation, prog_node: *std.Progress.Nod
         // We will invoke ourselves as a child process to gain access to LLD.
         // This is necessary because LLD does not behave properly as a library -
         // it calls exit() and does not reset all global data between invocations.
-        try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, "lld-link" });
+        const linker_command = "lld-link";
+        try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, linker_command });
 
         try argv.append("-ERRORLIMIT:0");
         try argv.append("-NOLOGO");
@@ -556,9 +557,7 @@ pub fn linkWithLLD(self: *Coff, comp: *Compilation, prog_node: *std.Progress.Nod
                 switch (term) {
                     .Exited => |code| {
                         if (code != 0) {
-                            // TODO parse this output and surface with the Compilation API rather than
-                            // directly outputting to stderr here.
-                            std.debug.print("{s}", .{stderr});
+                            comp.lockAndParseLldStderr(linker_command, stderr);
                             return error.LLDReportedFailure;
                         }
                     },
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index b6391b31c6..59f620f638 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -1422,7 +1422,8 @@ fn linkWithLLD(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !v
         // We will invoke ourselves as a child process to gain access to LLD.
         // This is necessary because LLD does not behave properly as a library -
         // it calls exit() and does not reset all global data between invocations.
-        try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, "ld.lld" });
+        const linker_command = "ld.lld";
+        try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, linker_command });
         if (is_obj) {
             try argv.append("-r");
         }
@@ -1841,9 +1842,7 @@ fn linkWithLLD(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !v
                 switch (term) {
                     .Exited => |code| {
                         if (code != 0) {
-                            // TODO parse this output and surface with the Compilation API rather than
-                            // directly outputting to stderr here.
-                            std.debug.print("{s}", .{stderr});
+                            comp.lockAndParseLldStderr(linker_command, stderr);
                             return error.LLDReportedFailure;
                         }
                     },
diff --git a/src/link/Wasm.zig b/src/link/Wasm.zig
index b9f2d74bd8..39f8a6bbe6 100644
--- a/src/link/Wasm.zig
+++ b/src/link/Wasm.zig
@@ -3125,7 +3125,8 @@ fn linkWithLLD(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) !
         // We will invoke ourselves as a child process to gain access to LLD.
         // This is necessary because LLD does not behave properly as a library -
         // it calls exit() and does not reset all global data between invocations.
-        try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, "wasm-ld" });
+        const linker_command = "wasm-ld";
+        try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, linker_command });
         try argv.append("--error-limit=0");
 
         if (wasm.base.options.lto) {
@@ -3357,9 +3358,7 @@ fn linkWithLLD(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) !
                 switch (term) {
                     .Exited => |code| {
                         if (code != 0) {
-                            // TODO parse this output and surface with the Compilation API rather than
-                            // directly outputting to stderr here.
-                            std.debug.print("{s}", .{stderr});
+                            comp.lockAndParseLldStderr(linker_command, stderr);
                             return error.LLDReportedFailure;
                         }
                     },