(Minor tweak) Make RegisterContextWindows_x86/x64::GetRegisterInfoAtIndex

return NULL for an invalid register.

The unwind logic asks for the "return address register" which doesn't exist
on x86/x86_64, returns -1 and calls this with -1 as a parameter, ends up 
out of scope of the array bounds for g_register_infos and later SIGSEGVs 
on accessing. This now matches the other GetRegisterInfoAtIndex for
other platforms.

llvm-svn: 271876

2 files changed, 9 insertions, 2 deletions

diff --git a/lldb/source/Plugins/Process/Windows/Common/x64/RegisterContextWindows_x64.cpp b/lldb/source/Plugins/Process/Windows/Common/x64/RegisterContextWindows_x64.cpp
index 103cff4a2a5..3a9c31a0b77 100644
--- a/lldb/source/Plugins/Process/Windows/Common/x64/RegisterContextWindows_x64.cpp
+++ b/lldb/source/Plugins/Process/Windows/Common/x64/RegisterContextWindows_x64.cpp
@@ -136,6 +136,8 @@ RegisterInfo g_register_infos[] = {
      nullptr},
 };
 
+static size_t k_num_register_infos = llvm::array_lengthof(g_register_infos);
+
 // Array of lldb register numbers used to define the set of all General Purpose Registers
 uint32_t g_gpr_reg_indices[] = {eRegisterIndexRax, eRegisterIndexRbx,   eRegisterIndexRcx, eRegisterIndexRdx,
                                 eRegisterIndexRdi, eRegisterIndexRsi,   eRegisterIndexR8,  eRegisterIndexR9,
@@ -169,7 +171,9 @@ RegisterContextWindows_x64::GetRegisterCount()
 const RegisterInfo *
 RegisterContextWindows_x64::GetRegisterInfoAtIndex(size_t reg)
 {
-    return &g_register_infos[reg];
+    if (reg < k_num_register_infos)
+        return &g_register_infos[reg];
+    return NULL;
 }
 
 size_t
diff --git a/lldb/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp b/lldb/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp
index a95561d20b9..11733eee7cb 100644
--- a/lldb/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp
+++ b/lldb/source/Plugins/Process/Windows/Common/x86/RegisterContextWindows_x86.cpp
@@ -64,6 +64,7 @@ RegisterInfo g_register_infos[] =
     { DEFINE_GPR(eip,    "pc"),     { ehframe_eip_i386,     dwarf_eip_i386,      LLDB_REGNUM_GENERIC_PC,    LLDB_INVALID_REGNUM,  lldb_eip_i386   },  nullptr,      nullptr},
     { DEFINE_GPR_BIN(eflags, "flags"), { ehframe_eflags_i386, dwarf_eflags_i386,   LLDB_REGNUM_GENERIC_FLAGS, LLDB_INVALID_REGNUM,  lldb_eflags_i386},  nullptr,      nullptr},
 };
+static size_t k_num_register_infos = llvm::array_lengthof(g_register_infos);
 
 // Array of lldb register numbers used to define the set of all General Purpose Registers
 uint32_t g_gpr_reg_indices[] =
@@ -106,7 +107,9 @@ RegisterContextWindows_x86::GetRegisterCount()
 const RegisterInfo *
 RegisterContextWindows_x86::GetRegisterInfoAtIndex(size_t reg)
 {
-    return &g_register_infos[reg];
+    if (reg < k_num_register_infos)
+        return &g_register_infos[reg];
+    return NULL;
 }
 
 size_t