Merge eb74a9d63d into f845fa04a0

Closes #21815.

lib/compiler/build_runner.zig

@@ -894,7 +894,7 @@ fn printStepFailure(
             try ttyconf.setColor(stderr, .reset);
         }
         try stderr.writeAll("\n");
-    } else if (s.result_error_msgs.items.len > 0) {
+    } else if (s.result_error_msgs.items.len > 0 or s.make_error_trace != null) {
         try ttyconf.setColor(stderr, .red);
         try stderr.writeAll(" failure\n");
         try ttyconf.setColor(stderr, .reset);
@@ -1103,7 +1103,7 @@ fn workerMakeOneStep(
     // No matter the result, we want to display error/warning messages.
     const show_compile_errors = !run.prominent_compile_errors and
         s.result_error_bundle.errorMessageCount() > 0;
-    const show_error_msgs = s.result_error_msgs.items.len > 0;
+    const show_error_msgs = s.result_error_msgs.items.len > 0 or s.make_error_trace != null;
     const show_stderr = s.result_stderr.len > 0;
 
     if (show_error_msgs or show_compile_errors or show_stderr) {
@@ -1217,6 +1217,14 @@ pub fn printErrorMessages(
         try stderr.writeAll(msg);
         try stderr.writeAll("\n");
     }
+
+    if (failing_step.make_error_trace) |make_err| {
+        try ttyconf.setColor(stderr, .red);
+        try stderr.writeAll("error: ");
+        try ttyconf.setColor(stderr, .reset);
+        try stderr.writer().print("this step's make function failed with error {s}", .{@errorName(make_err.err)});
+        if (make_err.trace) |trace| try trace.format("", .{}, stderr.writer());
+    }
 }
 
 fn steps(builder: *std.Build, out_stream: anytype) !void {

lib/std/Build/Step.zig

@@ -41,6 +41,8 @@ max_rss: usize,
 
 result_error_msgs: std.ArrayListUnmanaged([]const u8),
 result_error_bundle: std.zig.ErrorBundle,
+make_error_trace: ?MakeErrorTrace,
+
 result_stderr: []const u8,
 result_cached: bool,
 result_duration_ns: ?u64,
@@ -52,6 +54,12 @@ test_results: TestResults,
 /// to print along with debugging messages.
 debug_stack_trace: []usize,
 
+/// Storage for unhandled errors returned by the make function.
+pub const MakeErrorTrace = struct {
+    err: anyerror,
+    trace: ?*std.builtin.StackTrace,
+};
+
 pub const TestResults = struct {
     fail_count: u32 = 0,
     skip_count: u32 = 0,
@@ -214,6 +222,7 @@ pub fn init(options: StepOptions) Step {
         },
         .result_error_msgs = .{},
         .result_error_bundle = std.zig.ErrorBundle.empty,
+        .make_error_trace = null,
         .result_stderr = "",
         .result_cached = false,
         .result_duration_ns = null,
@@ -223,18 +232,20 @@ pub fn init(options: StepOptions) Step {
 }
 
 /// If the Step's `make` function reports `error.MakeFailed`, it indicates they
-/// have already reported the error. Otherwise, we add a simple error report
-/// here.
+/// have already reported the error. Otherwise, we store the error for reporting
+/// later.
 pub fn make(s: *Step, options: MakeOptions) error{ MakeFailed, MakeSkipped }!void {
     const arena = s.owner.allocator;
 
-    s.makeFn(s, options) catch |err| switch (err) {
+    s.makeFn(s, options) catch |err| {
+        switch (err) {
             error.MakeFailed => return error.MakeFailed,
             error.MakeSkipped => return error.MakeSkipped,
             else => {
-            s.result_error_msgs.append(arena, @errorName(err)) catch @panic("OOM");
+                s.make_error_trace = .{ .err = err, .trace = @errorReturnTrace() };
                 return error.MakeFailed;
             },
+        }
     };
 
     if (!s.test_results.isSuccess()) {
@@ -894,6 +905,7 @@ fn reset(step: *Step, gpa: Allocator) void {
 
     step.result_error_bundle.deinit(gpa);
     step.result_error_bundle = std.zig.ErrorBundle.empty;
+    step.make_error_trace = null;
 }
 
 /// Implementation detail of file watching. Prepares the step for being re-evaluated.

lib/std/debug/MemoryAccessor.zig

@@ -48,7 +48,8 @@ fn read(ma: *MemoryAccessor, address: usize, buf: []u8) bool {
                 switch (linux.E.init(bytes_read)) {
                     .SUCCESS => return bytes_read == buf.len,
                     .FAULT => return false,
-                    .INVAL, .PERM, .SRCH => unreachable, // own pid is always valid
+                    .INVAL, .SRCH => unreachable, // own pid is always valid
+                    .PERM => {}, // Known to happen in containers.
                     .NOMEM => {},
                     .NOSYS => {}, // QEMU is known not to implement this syscall.
                     else => unreachable, // unexpected