authorgravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2022-08-09 02:11:58-07:00
committergravatar for noreply@github.comGitHub <noreply@github.com> 2022-08-09 02:11:58-07:00
log85a3f9b0544c1b90a77ce26f99f9fc26116d756b
treea42093d83336a1dbbf90447154ec9e83dd2dcebf
parentc76b5c1a31ebe09726cd29e7a6da69613eabfd10
parentfeb90f6ed4f64eb0faef8fbbcf8c51fad5392b39
signaturebadge-question-mark Signed by PGP key 4AEE18F83AFDEB23

Merge pull request #12383 from ziglang/stage2-stack-traces

several improvements to error return tracing in the self-hosted compiler

4 files changed, 193 insertions(+), 24 deletions(-)

lib/std/builtin.zig+1-2
......@@ -867,10 +867,9 @@ pub fn panicOutOfBounds(index: usize, len: usize) noreturn {
867867 std.debug.panic("attempt to index out of bound: index {d}, len {d}", .{ index, len });
868868}
869869
870pub noinline fn returnError(maybe_st: ?*StackTrace) void {
870pub noinline fn returnError(st: *StackTrace) void {
871871 @setCold(true);
872872 @setRuntimeSafety(false);
873 const st = maybe_st orelse return;
874873 addErrRetTraceAddr(st, @returnAddress());
875874}
876875
src/AstGen.zig+52
......@@ -3070,6 +3070,19 @@ fn emitDbgNode(gz: *GenZir, node: Ast.Node.Index) !void {
30703070 const line = astgen.source_line - gz.decl_line;
30713071 const column = astgen.source_column;
30723072
3073 if (gz.instructions.items.len > 0) {
3074 const last = gz.instructions.items[gz.instructions.items.len - 1];
3075 const zir_tags = astgen.instructions.items(.tag);
3076 if (zir_tags[last] == .dbg_stmt) {
3077 const zir_datas = astgen.instructions.items(.data);
3078 zir_datas[last].dbg_stmt = .{
3079 .line = line,
3080 .column = column,
3081 };
3082 return;
3083 }
3084 }
3085
30733086 _ = try gz.add(.{ .tag = .dbg_stmt, .data = .{
30743087 .dbg_stmt = .{
30753088 .line = line,
......@@ -5050,6 +5063,16 @@ fn tryExpr(
50505063
50515064 if (parent_gz.in_defer) return astgen.failNode(node, "'try' not allowed inside defer expression", .{});
50525065
5066 // Ensure debug line/column information is emitted for this try expression.
5067 // Then we will save the line/column so that we can emit another one that goes
5068 // "backwards" because we want to evaluate the operand, but then put the debug
5069 // info back at the try keyword for error return tracing.
5070 if (!parent_gz.force_comptime) {
5071 try emitDbgNode(parent_gz, node);
5072 }
5073 const try_line = astgen.source_line - parent_gz.decl_line;
5074 const try_column = astgen.source_column;
5075
50535076 const operand_rl: ResultLoc = switch (rl) {
50545077 .ref => .ref,
50555078 else => .none,
......@@ -5079,6 +5102,7 @@ fn tryExpr(
50795102 };
50805103 const err_code = try else_scope.addUnNode(err_tag, operand, node);
50815104 try genDefers(&else_scope, &fn_block.base, scope, .{ .both = err_code });
5105 try emitDbgStmt(&else_scope, try_line, try_column);
50825106 _ = try else_scope.addUnNode(.ret_node, err_code, node);
50835107
50845108 try else_scope.setTryBody(try_inst, operand);
......@@ -6585,6 +6609,16 @@ fn ret(gz: *GenZir, scope: *Scope, node: Ast.Node.Index) InnerError!Zir.Inst.Ref
65856609
65866610 if (gz.in_defer) return astgen.failNode(node, "cannot return from defer expression", .{});
65876611
6612 // Ensure debug line/column information is emitted for this return expression.
6613 // Then we will save the line/column so that we can emit another one that goes
6614 // "backwards" because we want to evaluate the operand, but then put the debug
6615 // info back at the return keyword for error return tracing.
6616 if (!gz.force_comptime) {
6617 try emitDbgNode(gz, node);
6618 }
6619 const ret_line = astgen.source_line - gz.decl_line;
6620 const ret_column = astgen.source_column;
6621
65886622 const defer_outer = &astgen.fn_block.?.base;
65896623
65906624 const operand_node = node_datas[node].lhs;
......@@ -6603,11 +6637,13 @@ fn ret(gz: *GenZir, scope: *Scope, node: Ast.Node.Index) InnerError!Zir.Inst.Ref
66036637 const defer_counts = countDefers(astgen, defer_outer, scope);
66046638 if (!defer_counts.need_err_code) {
66056639 try genDefers(gz, defer_outer, scope, .both_sans_err);
6640 try emitDbgStmt(gz, ret_line, ret_column);
66066641 _ = try gz.addStrTok(.ret_err_value, err_name_str_index, ident_token);
66076642 return Zir.Inst.Ref.unreachable_value;
66086643 }
66096644 const err_code = try gz.addStrTok(.ret_err_value_code, err_name_str_index, ident_token);
66106645 try genDefers(gz, defer_outer, scope, .{ .both = err_code });
6646 try emitDbgStmt(gz, ret_line, ret_column);
66116647 _ = try gz.addUnNode(.ret_node, err_code, node);
66126648 return Zir.Inst.Ref.unreachable_value;
66136649 }
......@@ -6626,6 +6662,7 @@ fn ret(gz: *GenZir, scope: *Scope, node: Ast.Node.Index) InnerError!Zir.Inst.Ref
66266662 .never => {
66276663 // Returning a value that cannot be an error; skip error defers.
66286664 try genDefers(gz, defer_outer, scope, .normal_only);
6665 try emitDbgStmt(gz, ret_line, ret_column);
66296666 try gz.addRet(rl, operand, node);
66306667 return Zir.Inst.Ref.unreachable_value;
66316668 },
......@@ -6633,6 +6670,7 @@ fn ret(gz: *GenZir, scope: *Scope, node: Ast.Node.Index) InnerError!Zir.Inst.Ref
66336670 // Value is always an error. Emit both error defers and regular defers.
66346671 const err_code = if (rl == .ptr) try gz.addUnNode(.load, rl.ptr, node) else operand;
66356672 try genDefers(gz, defer_outer, scope, .{ .both = err_code });
6673 try emitDbgStmt(gz, ret_line, ret_column);
66366674 try gz.addRet(rl, operand, node);
66376675 return Zir.Inst.Ref.unreachable_value;
66386676 },
......@@ -6641,6 +6679,7 @@ fn ret(gz: *GenZir, scope: *Scope, node: Ast.Node.Index) InnerError!Zir.Inst.Ref
66416679 if (!defer_counts.have_err) {
66426680 // Only regular defers; no branch needed.
66436681 try genDefers(gz, defer_outer, scope, .normal_only);
6682 try emitDbgStmt(gz, ret_line, ret_column);
66446683 try gz.addRet(rl, operand, node);
66456684 return Zir.Inst.Ref.unreachable_value;
66466685 }
......@@ -6654,6 +6693,7 @@ fn ret(gz: *GenZir, scope: *Scope, node: Ast.Node.Index) InnerError!Zir.Inst.Ref
66546693 defer then_scope.unstack();
66556694
66566695 try genDefers(&then_scope, defer_outer, scope, .normal_only);
6696 try emitDbgStmt(&then_scope, ret_line, ret_column);
66576697 try then_scope.addRet(rl, operand, node);
66586698
66596699 var else_scope = gz.makeSubBlock(scope);
......@@ -6663,6 +6703,7 @@ fn ret(gz: *GenZir, scope: *Scope, node: Ast.Node.Index) InnerError!Zir.Inst.Ref
66636703 .both = try else_scope.addUnNode(.err_union_code, result, node),
66646704 };
66656705 try genDefers(&else_scope, defer_outer, scope, which_ones);
6706 try emitDbgStmt(&else_scope, ret_line, ret_column);
66666707 try else_scope.addRet(rl, operand, node);
66676708
66686709 try setCondBrPayload(condbr, is_non_err, &then_scope, 0, &else_scope, 0);
......@@ -11702,3 +11743,14 @@ fn countBodyLenAfterFixups(astgen: *AstGen, body: []const Zir.Inst.Index) u32 {
1170211743 }
1170311744 return @intCast(u32, count);
1170411745}
11746
11747fn emitDbgStmt(gz: *GenZir, line: u32, column: u32) !void {
11748 if (gz.force_comptime) return;
11749
11750 _ = try gz.add(.{ .tag = .dbg_stmt, .data = .{
11751 .dbg_stmt = .{
11752 .line = line,
11753 .column = column,
11754 },
11755 } });
11756}
src/Sema.zig+139-22
......@@ -14489,6 +14489,20 @@ fn zirBoolBr(
1448914489 const rhs_result = try sema.resolveBody(rhs_block, body, inst);
1449014490 _ = try rhs_block.addBr(block_inst, rhs_result);
1449114491
14492 return finishCondBr(sema, parent_block, &child_block, &then_block, &else_block, lhs, block_inst);
14493}
14494
14495fn finishCondBr(
14496 sema: *Sema,
14497 parent_block: *Block,
14498 child_block: *Block,
14499 then_block: *Block,
14500 else_block: *Block,
14501 cond: Air.Inst.Ref,
14502 block_inst: Air.Inst.Index,
14503) !Air.Inst.Ref {
14504 const gpa = sema.gpa;
14505
1449214506 try sema.air_extra.ensureUnusedCapacity(gpa, @typeInfo(Air.CondBr).Struct.fields.len +
1449314507 then_block.instructions.items.len + else_block.instructions.items.len +
1449414508 @typeInfo(Air.Block).Struct.fields.len + child_block.instructions.items.len + 1);
......@@ -14501,7 +14515,7 @@ fn zirBoolBr(
1450114515 sema.air_extra.appendSliceAssumeCapacity(else_block.instructions.items);
1450214516
1450314517 _ = try child_block.addInst(.{ .tag = .cond_br, .data = .{ .pl_op = .{
14504 .operand = lhs,
14518 .operand = cond,
1450514519 .payload = cond_br_payload,
1450614520 } } });
1450714521
......@@ -14871,10 +14885,83 @@ fn zirRetLoad(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Zir
1487114885 const operand = try sema.analyzeLoad(block, src, ret_ptr, src);
1487214886 return sema.analyzeRet(block, operand, src);
1487314887 }
14888
14889 if (sema.wantErrorReturnTracing()) {
14890 const is_non_err = try sema.analyzePtrIsNonErr(block, src, ret_ptr);
14891 return retWithErrTracing(sema, block, src, is_non_err, .ret_load, ret_ptr);
14892 }
14893
1487414894 _ = try block.addUnOp(.ret_load, ret_ptr);
1487514895 return always_noreturn;
1487614896}
1487714897
14898fn retWithErrTracing(
14899 sema: *Sema,
14900 block: *Block,
14901 src: LazySrcLoc,
14902 is_non_err: Air.Inst.Ref,
14903 ret_tag: Air.Inst.Tag,
14904 operand: Air.Inst.Ref,
14905) CompileError!Zir.Inst.Index {
14906 const need_check = switch (is_non_err) {
14907 .bool_true => {
14908 _ = try block.addUnOp(ret_tag, operand);
14909 return always_noreturn;
14910 },
14911 .bool_false => false,
14912 else => true,
14913 };
14914 const gpa = sema.gpa;
14915 const unresolved_stack_trace_ty = try sema.getBuiltinType(block, src, "StackTrace");
14916 const stack_trace_ty = try sema.resolveTypeFields(block, src, unresolved_stack_trace_ty);
14917 const ptr_stack_trace_ty = try Type.Tag.single_mut_pointer.create(sema.arena, stack_trace_ty);
14918 const err_return_trace = try block.addTy(.err_return_trace, ptr_stack_trace_ty);
14919 const return_err_fn = try sema.getBuiltin(block, src, "returnError");
14920 const args: [1]Air.Inst.Ref = .{err_return_trace};
14921
14922 if (!need_check) {
14923 _ = try sema.analyzeCall(block, return_err_fn, src, src, .never_inline, false, &args, null);
14924 _ = try block.addUnOp(ret_tag, operand);
14925 return always_noreturn;
14926 }
14927
14928 var then_block = block.makeSubBlock();
14929 defer then_block.instructions.deinit(gpa);
14930 _ = try then_block.addUnOp(ret_tag, operand);
14931
14932 var else_block = block.makeSubBlock();
14933 defer else_block.instructions.deinit(gpa);
14934 _ = try sema.analyzeCall(&else_block, return_err_fn, src, src, .never_inline, false, &args, null);
14935 _ = try else_block.addUnOp(ret_tag, operand);
14936
14937 try sema.air_extra.ensureUnusedCapacity(gpa, @typeInfo(Air.CondBr).Struct.fields.len +
14938 then_block.instructions.items.len + else_block.instructions.items.len +
14939 @typeInfo(Air.Block).Struct.fields.len + 1);
14940
14941 const cond_br_payload = sema.addExtraAssumeCapacity(Air.CondBr{
14942 .then_body_len = @intCast(u32, then_block.instructions.items.len),
14943 .else_body_len = @intCast(u32, else_block.instructions.items.len),
14944 });
14945 sema.air_extra.appendSliceAssumeCapacity(then_block.instructions.items);
14946 sema.air_extra.appendSliceAssumeCapacity(else_block.instructions.items);
14947
14948 _ = try block.addInst(.{ .tag = .cond_br, .data = .{ .pl_op = .{
14949 .operand = is_non_err,
14950 .payload = cond_br_payload,
14951 } } });
14952
14953 return always_noreturn;
14954}
14955
14956fn wantErrorReturnTracing(sema: *Sema) bool {
14957 // TODO implement this feature in all the backends and then delete this check.
14958 const backend_supports_error_return_tracing = sema.mod.comp.bin_file.options.use_llvm;
14959
14960 return sema.fn_ret_ty.isError() and
14961 sema.mod.comp.bin_file.options.error_return_tracing and
14962 backend_supports_error_return_tracing;
14963}
14964
1487814965fn addToInferredErrorSet(sema: *Sema, uncasted_operand: Air.Inst.Ref) !void {
1487914966 assert(sema.fn_ret_ty.zigTypeTag() == .ErrorUnion);
1488014967
......@@ -14920,27 +15007,15 @@ fn analyzeRet(
1492015007 return always_noreturn;
1492115008 }
1492215009
14923 // TODO implement this feature in all the backends and then delete this check.
14924 const backend_supports_error_return_tracing =
14925 sema.mod.comp.bin_file.options.use_llvm;
15010 try sema.resolveTypeLayout(block, src, sema.fn_ret_ty);
1492615011
14927 if (sema.fn_ret_ty.isError() and
14928 sema.mod.comp.bin_file.options.error_return_tracing and
14929 backend_supports_error_return_tracing)
14930 ret_err: {
14931 if (try sema.resolveMaybeUndefVal(block, src, operand)) |ret_val| {
14932 if (ret_val.tag() != .@"error") break :ret_err;
14933 }
14934 const return_err_fn = try sema.getBuiltin(block, src, "returnError");
14935 const unresolved_stack_trace_ty = try sema.getBuiltinType(block, src, "StackTrace");
14936 const stack_trace_ty = try sema.resolveTypeFields(block, src, unresolved_stack_trace_ty);
14937 const ptr_stack_trace_ty = try Type.Tag.optional_single_mut_pointer.create(sema.arena, stack_trace_ty);
14938 const err_return_trace = try block.addTy(.err_return_trace, ptr_stack_trace_ty);
14939 const args: [1]Air.Inst.Ref = .{err_return_trace};
14940 _ = try sema.analyzeCall(block, return_err_fn, src, src, .never_inline, false, &args, null);
15012 if (sema.wantErrorReturnTracing()) {
15013 // Avoid adding a frame to the error return trace in case the value is comptime-known
15014 // to be not an error.
15015 const is_non_err = try sema.analyzeIsNonErr(block, src, operand);
15016 return retWithErrTracing(sema, block, src, is_non_err, .ret, operand);
1494115017 }
1494215018
14943 try sema.resolveTypeLayout(block, src, sema.fn_ret_ty);
1494415019 _ = try block.addUnOp(.ret, operand);
1494515020 return always_noreturn;
1494615021}
......@@ -25418,6 +25493,27 @@ fn analyzeIsNull(
2541825493 return block.addUnOp(air_tag, operand);
2541925494}
2542025495
25496fn analyzePtrIsNonErrComptimeOnly(
25497 sema: *Sema,
25498 block: *Block,
25499 src: LazySrcLoc,
25500 operand: Air.Inst.Ref,
25501) CompileError!Air.Inst.Ref {
25502 const ptr_ty = sema.typeOf(operand);
25503 assert(ptr_ty.zigTypeTag() == .Pointer);
25504 const child_ty = ptr_ty.childType();
25505
25506 const child_tag = child_ty.zigTypeTag();
25507 if (child_tag != .ErrorSet and child_tag != .ErrorUnion) return Air.Inst.Ref.bool_true;
25508 if (child_tag == .ErrorSet) return Air.Inst.Ref.bool_false;
25509 assert(child_tag == .ErrorUnion);
25510
25511 _ = block;
25512 _ = src;
25513
25514 return Air.Inst.Ref.none;
25515}
25516
2542125517fn analyzeIsNonErrComptimeOnly(
2542225518 sema: *Sema,
2542325519 block: *Block,
......@@ -25431,10 +25527,16 @@ fn analyzeIsNonErrComptimeOnly(
2543125527 assert(ot == .ErrorUnion);
2543225528
2543325529 if (Air.refToIndex(operand)) |operand_inst| {
25434 const air_tags = sema.air_instructions.items(.tag);
25435 if (air_tags[operand_inst] == .wrap_errunion_payload) {
25436 return Air.Inst.Ref.bool_true;
25530 switch (sema.air_instructions.items(.tag)[operand_inst]) {
25531 .wrap_errunion_payload => return Air.Inst.Ref.bool_true,
25532 .wrap_errunion_err => return Air.Inst.Ref.bool_false,
25533 else => {},
2543725534 }
25535 } else if (operand == .undef) {
25536 return sema.addConstUndef(Type.bool);
25537 } else {
25538 // None of the ref tags can be errors.
25539 return Air.Inst.Ref.bool_true;
2543825540 }
2543925541
2544025542 const maybe_operand_val = try sema.resolveMaybeUndefVal(block, src, operand);
......@@ -25510,6 +25612,21 @@ fn analyzeIsNonErr(
2551025612 }
2551125613}
2551225614
25615fn analyzePtrIsNonErr(
25616 sema: *Sema,
25617 block: *Block,
25618 src: LazySrcLoc,
25619 operand: Air.Inst.Ref,
25620) CompileError!Air.Inst.Ref {
25621 const result = try sema.analyzePtrIsNonErrComptimeOnly(block, src, operand);
25622 if (result == .none) {
25623 try sema.requireRuntimeBlock(block, src, null);
25624 return block.addUnOp(.is_non_err_ptr, operand);
25625 } else {
25626 return result;
25627 }
25628}
25629
2551325630fn analyzeSlice(
2551425631 sema: *Sema,
2551525632 block: *Block,
test/stack_traces.zig+1
......@@ -22,6 +22,7 @@ pub fn addCases(cases: *tests.StackTracesContext) void {
2222 .ReleaseSafe = .{
2323 .exclude_os = .{
2424 .windows, // segfault
25 .linux, // defeated by aggressive inlining
2526 },
2627 .expect =
2728 \\error: TheSkyIsFalling