gdb/testsuite: DWARF assembler: add context parameters to _location

The _location proc is used to assemble a location description.  It needs
to know some contextual information:

- size of an address
- size of an offset (into another DWARF section)
- DWARF version

It currently get all this directly from global variables holding the
compilation unit information.  This is fine because as of now, all
location descriptions are generated in the context of creating a
compilation unit.  However, a subsequent patch will generate location
descriptions while generating a .debug_loclists section.  _location
should therefore no longer rely on the current compilation unit's
properties.

Change it to accept these values as parameters instead of accessing the
values for the CU.

No functional changes intended.

gdb/testsuite/ChangeLog:

	* lib/dwarf.exp (_location): Add parameters.
	(_handle_DW_FORM): Adjust.

Change-Id: Ib94981979c83ffbebac838081d645ad71c221637

2 files changed, 32 insertions, 13 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index ec385e5..e3166ad 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2021-02-02  Simon Marchi  <simon.marchi@efficios.com>
 
+	* lib/dwarf.exp (_location): Add parameters.
+	(_handle_DW_FORM): Adjust.
+
+2021-02-02  Simon Marchi  <simon.marchi@efficios.com>
+
 	PR gdb/26813
 	* lib/dwarf.exp (_handle_DW_FORM): Handle DW_FORM_rnglistx.
 	(cu): Generate header for DWARF 5.
diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp
index aba4afb..f4f1cab 100644
--- a/gdb/testsuite/lib/dwarf.exp
+++ b/gdb/testsuite/lib/dwarf.exp
@@ -515,11 +515,15 @@ namespace eval Dwarf {
 	    }
 
 	    SPECIAL_expr {
+		variable _cu_version
+		variable _cu_addr_size
+		variable _cu_offset_size
+
 		set l1 [new_label "expr_start"]
 		set l2 [new_label "expr_end"]
 		_op .uleb128 "$l2 - $l1" "expression"
 		define_label $l1
-		_location $value
+		_location $value $_cu_version $_cu_addr_size $_cu_offset_size
 		define_label $l2
 	    }
 
@@ -889,18 +893,28 @@ namespace eval Dwarf {
     # This is a miniature assembler for location expressions.  It is
     # suitable for use in the attributes to a DIE.  Its output is
     # prefixed with "=" to make it automatically use DW_FORM_block.
+    #
     # BODY is split by lines, and each line is taken to be a list.
+    #
+    # DWARF_VERSION is the DWARF version for the section where the location
+    # description is found.
+    #
+    # ADDR_SIZE is the length in bytes (4 or 8) of an address on the target
+    # machine (typically found in the header of the section where the location
+    # description is found).
+    #
+    # OFFSET_SIZE is the length in bytes (4 or 8) of an offset into a DWARF
+    # section.  This typically depends on whether 32-bit or 64-bit DWARF is
+    # used, as indicated in the header of the section where the location
+    # description is found.
+    #
     # (FIXME should use 'info complete' here.)
     # Each list's first element is the opcode, either short or long
     # forms are accepted.
     # FIXME argument handling
     # FIXME move docs
-    proc _location {body} {
+    proc _location { body dwarf_version addr_size offset_size } {
 	variable _constants
-	variable _cu_label
-	variable _cu_version
-	variable _cu_addr_size
-	variable _cu_offset_size
 
 	foreach line [split $body \n] {
 	    # Ignore blank lines, and allow embedded comments.
@@ -912,7 +926,7 @@ namespace eval Dwarf {
 
 	    switch -exact -- $opcode {
 		DW_OP_addr {
-		    _op .${_cu_addr_size}byte [lindex $line 1]
+		    _op .${addr_size}byte [lindex $line 1]
 		}
 
 		DW_OP_regx {
@@ -992,10 +1006,10 @@ namespace eval Dwarf {
 
 		    # Here label is a section offset.
 		    set label [lindex $line 1]
-		    if { $_cu_version == 2 } {
-			_op .${_cu_addr_size}byte $label
+		    if { $dwarf_version == 2 } {
+			_op .${addr_size}byte $label
 		    } else {
-			_op .${_cu_offset_size}byte $label
+			_op .${offset_size}byte $label
 		    }
 		    _op .sleb128 [lindex $line 2]
 		}
@@ -1007,10 +1021,10 @@ namespace eval Dwarf {
 
 		    # Here label is a section offset.
 		    set label [lindex $line 1]
-		    if { $_cu_version == 2 } {
-			_op .${_cu_addr_size}byte $label
+		    if { $dwarf_version == 2 } {
+			_op .${addr_size}byte $label
 		    } else {
-			_op .${_cu_offset_size}byte $label
+			_op .${offset_size}byte $label
 		    }
 		}