[PATCH] Fix: Sign extensions for DW_FORM_addrx were never considered

[Can Acar <canacar@imcan.dev>]

DW_FORM_addr is converted (sign-extended) to a signed value when
the dwarf size is less than the size of unrelocated_addr, if the
target architecture "naturally" sign extends an address (bfd.c).

However, the same handling was not done for DW_FORM_addrx. This
meant that for example, trying to `list` a function with an
address >= 0x80000000 on (some?) 32-bit mips targets, when
that address was encoded using DW_FORM_addrx, was broken.

This patch fixes this issue by plumbing read_addr_index_1 into
unit_head::read_address, which is the function used to extract
information from DW_FORM_addr, and so it handles this case
correctly.
---
 gdb/dwarf2/read.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 955893c5f0c..e83d6ca38ae 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -15350,12 +15350,14 @@ dwarf2_per_objfile::read_line_string (const gdb_byte *buf,
 
 static unrelocated_addr
 read_addr_index_1 (dwarf2_per_objfile *per_objfile, unsigned int addr_index,
-		   std::optional<ULONGEST> addr_base, int addr_size)
+		   std::optional<ULONGEST> addr_base, unit_head *cu_header)
 {
   struct objfile *objfile = per_objfile->objfile;
   bfd *abfd = objfile->obfd.get ();
   const gdb_byte *info_ptr;
   ULONGEST addr_base_or_zero = addr_base.has_value () ? *addr_base : 0;
+  unsigned int ignore_bytes_read;
+  unsigned char addr_size = cu_header->addr_size;
 
   per_objfile->per_bfd->addr.read (objfile);
   if (per_objfile->per_bfd->addr.buffer == NULL)
@@ -15368,10 +15370,7 @@ read_addr_index_1 (dwarf2_per_objfile *per_objfile, unsigned int addr_index,
 	   objfile_name (objfile));
   info_ptr = (per_objfile->per_bfd->addr.buffer + addr_base_or_zero
 	      + addr_index * addr_size);
-  if (addr_size == 4)
-    return (unrelocated_addr) bfd_get_32 (abfd, info_ptr);
-  else
-    return (unrelocated_addr) bfd_get_64 (abfd, info_ptr);
+  return cu_header->read_address(abfd, info_ptr, &ignore_bytes_read);
 }
 
 /* Given index ADDR_INDEX in .debug_addr, fetch the value.  */
@@ -15380,7 +15379,7 @@ static unrelocated_addr
 read_addr_index (struct dwarf2_cu *cu, unsigned int addr_index)
 {
   return read_addr_index_1 (cu->per_objfile, addr_index,
-			    cu->addr_base, cu->header.addr_size);
+			    cu->addr_base, &cu->header);
 }
 
 /* Given a pointer to an leb128 value, fetch the value from .debug_addr.  */
@@ -15403,9 +15402,9 @@ dwarf2_read_addr_index (dwarf2_per_cu *per_cu, dwarf2_per_objfile *per_objfile,
 {
   struct dwarf2_cu *cu = per_objfile->get_cu (per_cu);
   std::optional<ULONGEST> addr_base;
-  int addr_size;
+  unit_head *cu_header;
 
-  /* We need addr_base and addr_size.
+  /* We need addr_base and header (only some fields of which are used later).
      If we don't have PER_CU->cu, we have to get it.
      Nasty, but the alternative is storing the needed info in PER_CU,
      which at this point doesn't seem justified: it's not clear how frequently
@@ -15424,17 +15423,17 @@ dwarf2_read_addr_index (dwarf2_per_cu *per_cu, dwarf2_per_objfile *per_objfile,
   if (cu != NULL)
     {
       addr_base = cu->addr_base;
-      addr_size = cu->header.addr_size;
+      cu_header = &cu->header;
     }
   else
     {
       cutu_reader reader (*per_cu, *per_objfile, nullptr, nullptr, false,
 			  language_minimal);
       addr_base = reader.cu ()->addr_base;
-      addr_size = reader.cu ()->header.addr_size;
+      cu_header = &reader.cu ()->header;
     }
 
-  return read_addr_index_1 (per_objfile, addr_index, addr_base, addr_size);
+  return read_addr_index_1 (per_objfile, addr_index, addr_base, cu_header);
 }
 
 /* Given a DW_FORM_GNU_str_index value STR_INDEX, fetch the string.
-- 
2.50.1 (Apple Git-155)