Fix closed over variables not available in debuginfo for Windows MSVC
The issue was that the resulting debuginfo was too complex for LLVM to translate into CodeView records correctly. As a result, it simply ignored the debuginfo which meant Windows debuggers could not display any closed over variables when stepping inside a closure. This fixes that by spilling additional variables to the stack so that the resulting debuginfo is simple (just `*my_variable.dbg.spill`) and LLVM can generate the correct CV records.
This commit is contained in:
Wesley Wiser
parent
e9cdcccfa8
commit
533002d3a1
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@ -6,7 +6,7 @@ use rustc_middle::ty;
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use rustc_session::config::DebugInfo;
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use rustc_span::symbol::{kw, Symbol};
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use rustc_span::{BytePos, Span};
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use rustc_target::abi::{LayoutOf, Size};
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use rustc_target::abi::Size;
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use super::operand::{OperandRef, OperandValue};
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use super::place::PlaceRef;
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@ -265,33 +265,25 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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None => continue,
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};
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let mut layout = base.layout;
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let mut direct_offset = Size::ZERO;
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// FIXME(eddyb) use smallvec here.
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let mut indirect_offsets = vec![];
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let mut place = base;
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for elem in &var.projection[..] {
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match *elem {
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mir::ProjectionElem::Deref => {
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indirect_offsets.push(Size::ZERO);
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layout = bx.cx().layout_of(
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layout
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.ty
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.builtin_deref(true)
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.unwrap_or_else(|| {
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span_bug!(var.source_info.span, "cannot deref `{}`", layout.ty)
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})
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.ty,
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);
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place = place.project_deref(bx);
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}
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mir::ProjectionElem::Field(field, _) => {
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let i = field.index();
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let offset = indirect_offsets.last_mut().unwrap_or(&mut direct_offset);
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*offset += layout.fields.offset(i);
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layout = layout.field(bx.cx(), i);
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*offset += place.layout.fields.offset(i);
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place = place.project_field(bx, i);
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}
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mir::ProjectionElem::Downcast(_, variant) => {
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layout = layout.for_variant(bx.cx(), variant);
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place = place.project_downcast(bx, variant);
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}
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_ => span_bug!(
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var.source_info.span,
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@ -301,7 +293,39 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
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}
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}
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bx.dbg_var_addr(dbg_var, dbg_loc, base.llval, direct_offset, &indirect_offsets);
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// When targeting MSVC, create extra allocas for arguments instead of pointing multiple
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// dbg_var_addr() calls into the same alloca with offsets. MSVC uses CodeView records
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// not DWARF and LLVM doesn't support translating the resulting
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// [DW_OP_deref, DW_OP_plus_uconst, offset, DW_OP_deref] debug info to CodeView.
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// Creating extra allocas on the stack makes the resulting debug info simple enough
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// that LLVM can generate correct CodeView records and thus the values appear in the
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// debugger. (#83709)
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let should_create_individual_allocas = bx.cx().sess().target.is_like_msvc
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&& self.mir.local_kind(local) == mir::LocalKind::Arg
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// LLVM can handle simple things but anything more complex than just a direct
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// offset or one indirect offset of 0 is too complex for it to generate CV records
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// correctly.
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&& (direct_offset != Size::ZERO
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|| !matches!(&indirect_offsets[..], [Size::ZERO] | []));
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if should_create_individual_allocas {
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// Create a variable which will be a pointer to the actual value
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let ptr_ty = bx.tcx().mk_ty(ty::RawPtr(ty::TypeAndMut {
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mutbl: mir::Mutability::Mut,
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ty: place.layout.ty,
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}));
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let ptr_layout = bx.layout_of(ptr_ty);
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let alloca = PlaceRef::alloca(bx, ptr_layout);
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bx.set_var_name(alloca.llval, &(var.name.to_string() + ".dbg.spill"));
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// Write the pointer to the variable
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bx.store(place.llval, alloca.llval, alloca.align);
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// Point the debug info to `*alloca` for the current variable
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bx.dbg_var_addr(dbg_var, dbg_loc, alloca.llval, Size::ZERO, &[Size::ZERO]);
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} else {
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bx.dbg_var_addr(dbg_var, dbg_loc, base.llval, direct_offset, &indirect_offsets);
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}
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}
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}
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@ -402,6 +402,18 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
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downcast
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}
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pub fn project_deref<Bx: BuilderMethods<'a, 'tcx, Value = V>>(&self, bx: &mut Bx) -> Self {
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let target_ty = self.layout.ty.builtin_deref(true).expect("failed to deref");
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let layout = bx.layout_of(target_ty.ty);
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PlaceRef {
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llval: bx.load(self.llval, self.align),
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llextra: None,
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layout,
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align: layout.align.abi,
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}
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}
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pub fn storage_live<Bx: BuilderMethods<'a, 'tcx, Value = V>>(&self, bx: &mut Bx) {
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bx.lifetime_start(self.llval, self.layout.size);
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}
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@ -83,6 +83,55 @@
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// lldbr-check:(isize) closure_local = 8
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// lldb-command:continue
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// === CDB TESTS ===================================================================================
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// cdb-command: g
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// cdb-command: dx variable
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// cdb-check:variable : 1 [Type: [...]]
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// cdb-command: dx constant
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// cdb-check:constant : 2 [Type: [...]]
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// cdb-command: dx a_struct
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// cdb-check:a_struct [Type: var_captured_in_nested_closure::Struct]
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// cdb-check: [+0x[...]] a : -3 [Type: [...]]
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// cdb-check: [+0x[...]] b : 4.500000 [Type: [...]]
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// cdb-check: [+0x[...]] c : 0x5 [Type: unsigned [...]]
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// cdb-command: dx struct_ref
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// cdb-check:struct_ref : 0x[...] [Type: var_captured_in_nested_closure::Struct *]
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// cdb-check: [+0x[...]] a : -3 [Type: [...]]
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// cdb-check: [+0x[...]] b : 4.500000 [Type: [...]]
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// cdb-check: [+0x[...]] c : 0x5 [Type: unsigned [...]]
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// cdb-command: dx owned
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// cdb-check:owned : 0x[...] : 6 [Type: [...] *]
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// cdb-check: 6 [Type: [...]]
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// cdb-command: dx closure_local
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// cdb-check:closure_local : 8 [Type: [...]]
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// cdb-command: dx nested_closure
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// cdb-check:nested_closure [Type: var_captured_in_nested_closure::main::{{closure}}::closure-0]
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// cdb-command: g
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// cdb-command: dx variable
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// cdb-check:variable : 1 [Type: [...]]
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// cdb-command: dx constant
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// cdb-check:constant : 2 [Type: [...]]
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// cdb-command: dx a_struct
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// cdb-check:a_struct [Type: var_captured_in_nested_closure::Struct]
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// cdb-check: [+0x[...]] a : -3 [Type: [...]]
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// cdb-check: [+0x[...]] b : 4.500000 [Type: [...]]
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// cdb-check: [+0x[...]] c : 0x5 [Type: unsigned [...]]
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// cdb-command: dx struct_ref
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// cdb-check:struct_ref : 0x[...] [Type: var_captured_in_nested_closure::Struct *]
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// cdb-check: [+0x[...]] a : -3 [Type: [...]]
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// cdb-check: [+0x[...]] b : 4.500000 [Type: [...]]
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// cdb-check: [+0x[...]] c : 0x5 [Type: unsigned [...]]
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// cdb-command: dx owned
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// cdb-check:owned : 0x[...] : 6 [Type: [...] *]
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// cdb-check: 6 [Type: [...]]
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// cdb-command: dx closure_local
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// cdb-check:closure_local : 8 [Type: [...]]
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#![allow(unused_variables)]
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#![feature(box_syntax)]
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#![feature(omit_gdb_pretty_printer_section)]
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@ -73,6 +73,48 @@
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// lldbg-check:[...]$9 = 6
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// lldbr-check:(isize) *owned = 6
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// === CDB TESTS ===================================================================================
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// cdb-command: g
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// cdb-command: dx variable
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// cdb-check:variable : 1 [Type: [...]]
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// cdb-command: dx constant
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// cdb-check:constant : 2 [Type: [...]]
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// cdb-command: dx a_struct
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// cdb-check:a_struct [Type: var_captured_in_stack_closure::Struct]
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// cdb-check: [+0x[...]] a : -3 [Type: [...]]
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// cdb-check: [+0x[...]] b : 4.500000 [Type: [...]]
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// cdb-check: [+0x[...]] c : 0x5 [Type: unsigned [...]]
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// cdb-command: dx struct_ref
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// cdb-check:struct_ref : 0x[...] [Type: var_captured_in_stack_closure::Struct *]
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// cdb-check: [+0x[...]] a : -3 [Type: [...]]
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// cdb-check: [+0x[...]] b : 4.500000 [Type: [...]]
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// cdb-check: [+0x[...]] c : 0x5 [Type: unsigned [...]]
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// cdb-command: dx owned
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// cdb-check:owned : 0x[...] : 6 [Type: [...] *]
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// cdb-command: g
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// cdb-command: dx variable
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// cdb-check:variable : 2 [Type: [...]]
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// cdb-command: dx constant
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// cdb-check:constant : 2 [Type: [...]]
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// cdb-command: dx a_struct
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// cdb-check:a_struct [Type: var_captured_in_stack_closure::Struct]
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// cdb-check: [+0x[...]] a : -3 [Type: [...]]
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// cdb-check: [+0x[...]] b : 4.500000 [Type: [...]]
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// cdb-check: [+0x[...]] c : 0x5 [Type: unsigned [...]]
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// cdb-command: dx struct_ref
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// cdb-check:struct_ref : 0x[...] [Type: var_captured_in_stack_closure::Struct *]
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// cdb-check: [+0x[...]] a : -3 [Type: [...]]
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// cdb-check: [+0x[...]] b : 4.500000 [Type: [...]]
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// cdb-check: [+0x[...]] c : 0x5 [Type: unsigned [...]]
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// cdb-command: dx owned
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// cdb-check:owned : 0x[...] : 6 [Type: [...] *]
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#![feature(box_syntax)]
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#![allow(unused_variables)]
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#![feature(omit_gdb_pretty_printer_section)]
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