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elf: implement slice types in debug info
Implements slice types including `[]const u8` for passing as
formal parameters in DWARF. Breaking on a function accepting
a slice in `gdb` will now yield the same behavior as stage1 and/or
LLVM backend:
```zig
fn sumArrayLens(a: []const u32, b: []const u8) usize {
return a.len + b.len;
}
```
Both `a` and `b` can now be inspected in the debugger:
```
Breakpoint 1, sumArrayLens (a=..., b=...) at arr.zig:59
(gdb) p a
$1 = {ptr = 0x7fffffff685c, len = 5}
(gdb) p b
$2 = {ptr = 0x7fffffff683d "\252\252\252\\h\377\377\377\177", len = 3}
(gdb)
```
This commit is contained in:
Jakub Konka
parent
aa4eaea778
commit
4192be8403
@ -784,8 +784,10 @@ pub const abbrev_subprogram = 2;
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pub const abbrev_subprogram_retvoid = 3;
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pub const abbrev_base_type = 4;
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pub const abbrev_ptr_type = 5;
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pub const abbrev_pad1 = 6;
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pub const abbrev_parameter = 7;
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pub const abbrev_anon_struct_type = 6;
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pub const abbrev_struct_member = 7;
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pub const abbrev_pad1 = 8;
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pub const abbrev_parameter = 9;
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pub fn flush(self: *Elf, comp: *Compilation) !void {
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if (self.base.options.emit == null) {
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@ -882,6 +884,24 @@ pub fn flushModule(self: *Elf, comp: *Compilation) !void {
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DW.FORM.ref4,
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0,
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0, // table sentinel
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abbrev_anon_struct_type,
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DW.TAG.structure_type,
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DW.CHILDREN.yes, // header
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DW.AT.byte_size,
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DW.FORM.sdata,
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0,
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0, // table sentinel
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abbrev_struct_member,
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DW.TAG.member,
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DW.CHILDREN.no, // header
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DW.AT.name,
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DW.FORM.string,
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DW.AT.type,
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DW.FORM.ref4,
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DW.AT.data_member_location,
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DW.FORM.sdata,
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0,
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0, // table sentinel
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abbrev_pad1,
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DW.TAG.unspecified_type,
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DW.CHILDREN.no, // header
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@ -2395,6 +2415,16 @@ fn finishUpdateDecl(
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dbg_info_type_relocs: *File.DbgInfoTypeRelocsTable,
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dbg_info_buffer: *std.ArrayList(u8),
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) !void {
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// We need this for the duration of this function only so that for composite
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// types such as []const u32, if the type *u32 is non-existent, we create
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// it synthetically and store the backing bytes in this arena. After we are
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// done with the relocations, we can safely deinit the entire memory slab.
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// TODO currently, we do not store the relocations for future use, however,
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// if that is the case, we should move memory management to a higher scope,
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// such as linker scope, or whatnot.
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var dbg_type_arena = std.heap.ArenaAllocator.init(self.base.allocator);
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defer dbg_type_arena.deinit();
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// Now we emit the .debug_info types of the Decl. These will count towards the size of
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// the buffer, so we have to do it before computing the offset, and we can't perform the actual
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// relocations yet.
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@ -2404,7 +2434,7 @@ fn finishUpdateDecl(
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const ty = dbg_info_type_relocs.keys()[it];
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const value_ptr = dbg_info_type_relocs.getPtr(ty).?;
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value_ptr.off = @intCast(u32, dbg_info_buffer.items.len);
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try self.addDbgInfoType(ty, dbg_info_buffer, dbg_info_type_relocs);
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try self.addDbgInfoType(dbg_type_arena.allocator(), ty, dbg_info_buffer, dbg_info_type_relocs);
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}
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}
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@ -2721,11 +2751,12 @@ pub fn updateDecl(self: *Elf, module: *Module, decl: *Module.Decl) !void {
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/// Asserts the type has codegen bits.
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fn addDbgInfoType(
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self: *Elf,
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arena: Allocator,
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ty: Type,
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dbg_info_buffer: *std.ArrayList(u8),
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dbg_info_type_relocs: *File.DbgInfoTypeRelocsTable,
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) error{OutOfMemory}!void {
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var reloc: ?struct { ty: Type, reloc: u32 } = null;
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var relocs = std.ArrayList(struct { ty: Type, reloc: u32 }).init(arena);
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switch (ty.zigTypeTag()) {
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.Void => unreachable,
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@ -2767,17 +2798,48 @@ fn addDbgInfoType(
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try dbg_info_buffer.append(abbrev_pad1);
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}
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},
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.Pointer => blk: {
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.Pointer => {
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if (ty.isSlice()) {
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log.debug("TODO implement .debug_info for type '{}'", .{ty});
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try dbg_info_buffer.append(abbrev_pad1);
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break :blk;
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// Slices are anonymous structs: struct { .ptr = *, .len = N }
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try dbg_info_buffer.ensureUnusedCapacity(23);
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// DW.AT.structure_type
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dbg_info_buffer.appendAssumeCapacity(abbrev_anon_struct_type);
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// DW.AT.byte_size, DW.FORM.sdata
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dbg_info_buffer.appendAssumeCapacity(16);
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// DW.AT.member
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dbg_info_buffer.appendAssumeCapacity(abbrev_struct_member);
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// DW.AT.name, DW.FORM.string
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dbg_info_buffer.appendSliceAssumeCapacity("ptr");
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dbg_info_buffer.appendAssumeCapacity(0);
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// DW.AT.type, DW.FORM.ref4
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var index = dbg_info_buffer.items.len;
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try dbg_info_buffer.resize(index + 4);
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var buf = try arena.create(Type.SlicePtrFieldTypeBuffer);
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const ptr_ty = ty.slicePtrFieldType(buf);
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try relocs.append(.{ .ty = ptr_ty, .reloc = @intCast(u32, index) });
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// DW.AT.data_member_location, DW.FORM.sdata
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dbg_info_buffer.appendAssumeCapacity(0);
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// DW.AT.member
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dbg_info_buffer.appendAssumeCapacity(abbrev_struct_member);
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// DW.AT.name, DW.FORM.string
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dbg_info_buffer.appendSliceAssumeCapacity("len");
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dbg_info_buffer.appendAssumeCapacity(0);
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// DW.AT.type, DW.FORM.ref4
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index = dbg_info_buffer.items.len;
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try dbg_info_buffer.resize(index + 4);
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try relocs.append(.{ .ty = Type.initTag(.usize), .reloc = @intCast(u32, index) });
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// DW.AT.data_member_location, DW.FORM.sdata
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dbg_info_buffer.appendAssumeCapacity(8);
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// DW.AT.structure_type delimit children
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dbg_info_buffer.appendAssumeCapacity(0);
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} else {
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try dbg_info_buffer.ensureUnusedCapacity(5);
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dbg_info_buffer.appendAssumeCapacity(abbrev_ptr_type);
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// DW.AT.type, DW.FORM.ref4
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const index = dbg_info_buffer.items.len;
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try dbg_info_buffer.resize(index + 4);
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try relocs.append(.{ .ty = ty.childType(), .reloc = @intCast(u32, index) });
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}
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try dbg_info_buffer.ensureUnusedCapacity(5);
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dbg_info_buffer.appendAssumeCapacity(abbrev_ptr_type);
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const index = dbg_info_buffer.items.len;
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try dbg_info_buffer.resize(index + 4); // DW.AT.type, DW.FORM.ref4
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reloc = .{ .ty = ty.childType(), .reloc = @intCast(u32, index) };
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},
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else => {
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log.debug("TODO implement .debug_info for type '{}'", .{ty});
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@ -2785,7 +2847,7 @@ fn addDbgInfoType(
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},
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}
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if (reloc) |rel| {
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for (relocs.items) |rel| {
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const gop = try dbg_info_type_relocs.getOrPut(self.base.allocator, rel.ty);
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if (!gop.found_existing) {
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gop.value_ptr.* = .{
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