[PATCH] libdw: Handle DW_OP_GNU_uninit in dwarf_getlocation

[PATCH] libdw: Handle DW_OP_GNU_uninit in dwarf_getlocation

[Mark Wielaard]

dwarf_getlocation would return an error when it saw a
DW_OP_GNU_uninit. Handle it by simply recognizing as a no argument
operation.

DW_OP_GNU_uninit is emitted by GCC as a marker to flag the location
expression as referring to an uninitialized value.

Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdw/ChangeLog           | 5 +++++
 libdw/dwarf_getlocation.c | 1 +
 tests/ChangeLog           | 4 ++++
 tests/varlocs.c           | 6 ++++++
 4 files changed, 16 insertions(+)

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 71e96c88..9bea831e 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,8 @@
+2023-02-10  Mark Wielaard  <mark@klomp.org>
+
+	* dwarf_getlocation.c (__libdw_intern_expression): Handle
+	DW_OP_GNU_uninit.
+
 2023-01-22  Mark Wielaard  <mark@klomp.org>
 
 	* dwarf_getscopes.c (pc_record): Return nscopes when done.
diff --git a/libdw/dwarf_getlocation.c b/libdw/dwarf_getlocation.c
index d0d78163..553fdc98 100644
--- a/libdw/dwarf_getlocation.c
+++ b/libdw/dwarf_getlocation.c
@@ -396,6 +396,7 @@ __libdw_intern_expression (Dwarf *dbg, bool other_byte_order,
 	case DW_OP_form_tls_address:
 	case DW_OP_GNU_push_tls_address:
 	case DW_OP_stack_value:
+	case DW_OP_GNU_uninit:
 	  /* No operand.  */
 	  break;
 
diff --git a/tests/ChangeLog b/tests/ChangeLog
index 974a3a4f..fd261bc6 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,7 @@
+2023-02-10  Mark Wielaard  <mark@klomp.org>
+
+	* varlocs.c (print_expr): Handle DW_OP_GNU_uninit.
+
 2023-02-03  Mark Wielaard  <mark@klomp.org>
 
 	* run-addr2line-C-test.sh: Check ELFUTILS_DISABLE_DEMANGLE.
diff --git a/tests/varlocs.c b/tests/varlocs.c
index d2c13767..8e563fd3 100644
--- a/tests/varlocs.c
+++ b/tests/varlocs.c
@@ -251,6 +251,12 @@ print_expr (Dwarf_Attribute *attr, Dwarf_Op *expr, Dwarf_Addr addr, int depth)
       printf ("%s", opname);
       break;
 
+    case DW_OP_GNU_uninit:
+      /* No arguments. Special. It means the expression describes
+	 an value which hasn't been initialized (yet).  */
+      printf ("%s", opname);
+      break;
+
     case DW_OP_call_frame_cfa:
       /* No arguments. Special. Pushes Call Frame Address as computed
 	 by CFI data (dwarf_cfi_addrframe will fetch that info (either from
-- 
2.39.1

Re: [PATCH] libdw: Handle DW_OP_GNU_uninit in dwarf_getlocation

[Mark Wielaard]

Hi,

On Fri, 2023-02-10 at 14:01 +0100, Mark Wielaard wrote:
> dwarf_getlocation would return an error when it saw a
> DW_OP_GNU_uninit. Handle it by simply recognizing as a no argument
> operation.
> 
> DW_OP_GNU_uninit is emitted by GCC as a marker to flag the location
> expression as referring to an uninitialized value.

I pushed this.

Cheers,

Mark