Fix BZ15121 -- x/a broken for addresses in shared libraries (try #2)

[Paul Pluzhnikov]

Greetings,

Attached is my second attempt to fix BZ15121. Tested on Linux/x86_64;
no new failures.

Previous attempt:
https://sourceware.org/ml/gdb-patches/2015-09/msg00074.html

The change to long_long.exp needs to be made conditional (i.e. use old
pattern on MIPS and SH; new pattern everywhere else). I am not sure how
to achieve that. Should I make it conditional on 'istarget "mips*"' or ... ?


Thanks,


2016-10-10  Paul Pluzhnikov  <ppluzhnikov@google.com>

        [BZ #15121]
        * gdb/gdbarch.h (gdbarch_sign_extend_vma): New.
        (set_gdbarch_sign_extend_vma): New.
        * gdb/gdbarch.c (struct gdbarch): Add sign_extend_vma.
        (gdbarch_sign_extend_vma, set_gdbarch_sign_extend_vma): New.
        (gdbarch_find_by_info): Set sign_extend_vma from BFD.
        * gdb/value.c (unpack_pointer): Don't sign-extend when necessary.

testsuite/ChangeLog:

2016-10-10  Paul Pluzhnikov  <ppluzhnikov@google.com>

        [BZ #15121]
        * gdb.base/long_long.exp: Adjust.


-- 
Paul Pluzhnikov
-------------- next part --------------
diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
index 4d8ef18..fd46892 100644
--- a/gdb/gdbarch.c
+++ b/gdb/gdbarch.c
@@ -130,6 +130,7 @@ struct gdbarch
   enum bfd_endian byte_order_for_code;
   enum gdb_osabi osabi;
   const struct target_desc * target_desc;
+  int sign_extend_vma;
 
   /* target specific vector.  */
   struct gdbarch_tdep *tdep;
@@ -4918,6 +4919,17 @@ set_gdbarch_addressable_memory_unit_size (struct gdbarch *gdbarch,
   gdbarch->addressable_memory_unit_size = addressable_memory_unit_size;
 }
 
+int
+gdbarch_sign_extend_vma (struct gdbarch *gdbarch)
+{
+  return gdbarch->sign_extend_vma;
+}
+
+void
+set_gdbarch_sign_extend_vma (struct gdbarch *gdbarch, int value)
+{
+  gdbarch->sign_extend_vma = value;
+}
 
 /* Keep a registry of per-architecture data-pointers required by GDB
    modules.  */
@@ -5234,6 +5246,11 @@ gdbarch_find_by_info (struct gdbarch_info info)
       return NULL;
     }
 
+  /* We do this every time because on the first call we may not yet have
+     abfd available.  */
+  new_gdbarch->sign_extend_vma = info.abfd == NULL ?
+    0 : bfd_get_sign_extend_vma (info.abfd);
+
   /* Is this a pre-existing architecture (as determined by already
      being initialized)?  Move it to the front of the architecture
      list (keeping the list sorted Most Recently Used).  */
diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
index cd01718..26dbf03 100644
--- a/gdb/gdbarch.h
+++ b/gdb/gdbarch.h
@@ -1530,6 +1530,9 @@ typedef int (gdbarch_addressable_memory_unit_size_ftype) (struct gdbarch *gdbarc
 extern int gdbarch_addressable_memory_unit_size (struct gdbarch *gdbarch);
 extern void set_gdbarch_addressable_memory_unit_size (struct gdbarch *gdbarch, gdbarch_addressable_memory_unit_size_ftype *addressable_memory_unit_size);
 
+extern int gdbarch_sign_extend_vma (struct gdbarch *gdbarch);
+extern void set_gdbarch_sign_extend_vma (struct gdbarch *gdbarch, int sign_extend_vma);
+
 /* Definition for an unknown syscall, used basically in error-cases.  */
 #define UNKNOWN_SYSCALL (-1)
 
diff --git a/gdb/testsuite/gdb.base/long_long.exp b/gdb/testsuite/gdb.base/long_long.exp
index ab47374..8f48266 100644
--- a/gdb/testsuite/gdb.base/long_long.exp
+++ b/gdb/testsuite/gdb.base/long_long.exp
@@ -249,7 +249,7 @@ gdb_test "x/2bd b" "1.*-89"
 gdb_test "x/2bu b" "1.*167"
 gdb_test "x/2bo b" "01.*0247"
 gdb_test "x/2bt b" "00000001.*10100111"
-gdb_test_ptr "x/2ba b" "" "" "0x1.*0xffffffa7" "0x1.*0xffffffffffffffa7"
+gdb_test_ptr "x/2ba b" "" "" "0x1.*0xa7" "0x1.*0xa7"
 gdb_test "x/2bc b" "1 '.001'.*-89 '.\[0-9\]*'"
 gdb_test "x/2bf b" "1.*-89"
 
@@ -258,7 +258,7 @@ gdb_test "x/2hd h" "291.*-22738"
 gdb_test "x/2hu h" "291.*42798"
 gdb_test "x/2ho h" "0443.*0123456"
 gdb_test "x/2ht h" "0000000100100011.*1010011100101110"
-gdb_test_ptr "x/2ha h" "" ""  "0x123.*0xffffa72e" "0x123.*0xffffffffffffa72e"
+gdb_test_ptr "x/2ha h" "" ""  "0x123.*0xa72e" "0x123.*0xa72e"
 gdb_test "x/2hc h" "35 '.'.*46 '.'"
 gdb_test "x/2hf h" "291.*-22738"
 
@@ -267,7 +267,7 @@ gdb_test "x/2wd w" "19088743.*-1490098887"
 gdb_test "x/2wu w" "19088743.*2804868409"
 gdb_test "x/2wo w" "0110642547.*024713562471"
 gdb_test "x/2wt w" "00000001001000110100010101100111.*10100111001011101110010100111001"
-gdb_test_ptr "x/2wa w" "" ""  "0x1234567.*0xa72ee539" "0x1234567.*0xffffffffa72ee539"
+gdb_test_ptr "x/2wa w" "" ""  "0x1234567.*0xa72ee539" "0x1234567.*0xa72ee539"
 gdb_test "x/2wc w" "103 'g'.*57 '9'"
 gdb_test "x/2wf w" "2.99881655e-0?38.*-2.42716126e-0?15"
 
diff --git a/gdb/value.c b/gdb/value.c
index b825aec..9c38cfe 100644
--- a/gdb/value.c
+++ b/gdb/value.c
@@ -3040,7 +3040,17 @@ unpack_pointer (struct type *type, const gdb_byte *valaddr)
 {
   /* Assume a CORE_ADDR can fit in a LONGEST (for now).  Not sure
      whether we want this to be true eventually.  */
-  return unpack_long (type, valaddr);
+  const LONGEST ret = unpack_long (type, valaddr);
+  const int len = TYPE_LENGTH (type);
+
+  if (sizeof (CORE_ADDR) > len && ret < 0) {
+    struct gdbarch *arch = get_type_arch (type);
+
+    if (!gdbarch_sign_extend_vma (arch))
+      /* Don't sign-extend 32-bit pointer.  BZ 15121.  */
+      return ret & ((1UL << (8 * len)) - 1);
+  }
+  return ret;
 }