[Lldb-commits] [lldb] 1f7a93d - [lldb][Windows] Fix "Invalid register name" for eax on x86_64 attach (#203498)

[via lldb-commits]

Author: Charles Zablit
Date: 2026-06-30T23:49:47+01:00
New Revision: 1f7a93d088f0b8549156aa2d4a241cdf8e36a066

URL: https://github.com/llvm/llvm-project/commit/1f7a93d088f0b8549156aa2d4a241cdf8e36a066
DIFF: https://github.com/llvm/llvm-project/commit/1f7a93d088f0b8549156aa2d4a241cdf8e36a066.diff

LOG: [lldb][Windows] Fix "Invalid register name" for eax on x86_64 attach (#203498)

On Windows, when attaching to a process with no pre-existing target,
lldb reports "Invalid register name" for sub-registers like eax.

This is due to a bug in `ABIX86::AugmentRegisterInfo`, which determines
the GPR base size by reading
`Target::GetArchitecture().GetAddressByteSize()`. During attach, the
target's architecture has not yet been set when `AugmentRegisterInfo`
runs, so the lookup returns 0, the process is treated as 32-bit, and the
x86_64 sub-registers are never added.

This patch removes the dependency on the target's architecture: the X86
ABI plugins already know their own bitness, so `ABIX86_64` and
`ABIX86_i386` now report it directly via a new `Is64Bit()` virtual.

This patch fixes
`TestRegisters::test_convenience_registers_with_process_attach` and
`TestRegisters::test_convenience_registers_16bit_with_process_attach` on
Windows using `LLDB_USE_LLDB_SERVER=1`.

rdar://180307995

Added: 
    

Modified: 
    lldb/source/Plugins/ABI/X86/ABIX86.cpp
    lldb/source/Plugins/ABI/X86/ABIX86.h
    lldb/source/Plugins/ABI/X86/ABIX86_64.h
    lldb/source/Plugins/ABI/X86/ABIX86_i386.h

Removed: 
    


################################################################################
diff  --git a/lldb/source/Plugins/ABI/X86/ABIX86.cpp b/lldb/source/Plugins/ABI/X86/ABIX86.cpp
index db170700d3f65..de7eefab58d1b 100644
--- a/lldb/source/Plugins/ABI/X86/ABIX86.cpp
+++ b/lldb/source/Plugins/ABI/X86/ABIX86.cpp
@@ -205,11 +205,10 @@ void ABIX86::AugmentRegisterInfo(
   if (!process_sp)
     return;
 
-  uint32_t gpr_base_size =
-      process_sp->GetTarget().GetArchitecture().GetAddressByteSize();
+  uint32_t gpr_base_size = Is64Bit() ? 8 : 4;
 
   // primary map from a base register to its subregisters
-  BaseRegToRegsMap base_reg_map = makeBaseRegMap(gpr_base_size == 8);
+  BaseRegToRegsMap base_reg_map = makeBaseRegMap(Is64Bit());
   // set used for fast matching of register names to subregisters
   llvm::SmallDenseSet<llvm::StringRef, 64> subreg_name_set;
   // convenience array providing access to all subregisters of given kind,

diff  --git a/lldb/source/Plugins/ABI/X86/ABIX86.h b/lldb/source/Plugins/ABI/X86/ABIX86.h
index 1114084fbc5d8..05985c9e1f5b1 100644
--- a/lldb/source/Plugins/ABI/X86/ABIX86.h
+++ b/lldb/source/Plugins/ABI/X86/ABIX86.h
@@ -21,6 +21,8 @@ class ABIX86 : public lldb_private::MCBasedABI {
   void AugmentRegisterInfo(
       std::vector<lldb_private::DynamicRegisterInfo::Register> &regs) override;
 
+  virtual bool Is64Bit() const = 0;
+
 private:
   using lldb_private::MCBasedABI::MCBasedABI;
 };

diff  --git a/lldb/source/Plugins/ABI/X86/ABIX86_64.h b/lldb/source/Plugins/ABI/X86/ABIX86_64.h
index 8fc98507adeeb..761f0670bc860 100644
--- a/lldb/source/Plugins/ABI/X86/ABIX86_64.h
+++ b/lldb/source/Plugins/ABI/X86/ABIX86_64.h
@@ -18,6 +18,8 @@ class ABIX86_64 : public ABIX86 {
     return name;
   }
 
+  bool Is64Bit() const override { return true; }
+
 private:
   using ABIX86::ABIX86;
 };

diff  --git a/lldb/source/Plugins/ABI/X86/ABIX86_i386.h b/lldb/source/Plugins/ABI/X86/ABIX86_i386.h
index cb3baa5150fc3..feb92dbc6d5e1 100644
--- a/lldb/source/Plugins/ABI/X86/ABIX86_i386.h
+++ b/lldb/source/Plugins/ABI/X86/ABIX86_i386.h
@@ -15,6 +15,9 @@ class ABIX86_i386 : public ABIX86 {
 public:
   uint32_t GetGenericNum(llvm::StringRef name) override;
 
+protected:
+  bool Is64Bit() const override { return false; }
+
 private:
   using ABIX86::ABIX86;
 };