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std.debug.Dwarf.Unwind: deal with invalid def_cfa_reg by GNU toolchains

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Alex Rønne Petersen 2025-10-02 03:05:33 +02:00
parent 97de46dc16
commit a4f95b1e61
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1 changed files with 12 additions and 1 deletions
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13
lib/std/debug/Dwarf/Unwind/VirtualMachine.zig
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@ -256,7 +256,18 @@ fn evalInstructions(
.offset = cfa.offset_sf * cie.data_alignment_factor,
} },
.def_cfa_reg => |register| switch (vm.current_row.cfa) {
.none, .expression => return error.InvalidOperation,
.none => {
// According to the DWARF specification, this is not valid, because this
// instruction can only be used to replace the register if the rule is already a
// `.reg_off`. However, this is emitted in practice by GNU toolchains for some
// targets, and so by convention is interpreted as equivalent to `.def_cfa` with
// an offset of 0.
vm.current_row.cfa = .{ .reg_off = .{
.register = register,
.offset = 0,
} };
},
.expression => return error.InvalidOperation,
.reg_off => |*ro| ro.register = register,
},
.def_cfa_offset => |offset| switch (vm.current_row.cfa) {