[RFC-v2] Allow explicit 16 or 32 char in 'x /s'

Pierre Muller
2010-03-31T16:11:51Z

> -----Message d'origine-----
> De : gdb-patches-owner@sourceware.org [mailto:gdb-patches-
> owner@sourceware.org] De la part de Tom Tromey
> Envoyé : Tuesday, March 30, 2010 10:33 PM
> À : Pierre Muller
> Cc : 'Eli Zaretskii'; gdb-patches@sourceware.org
> Objet : Re: [RFC] Allow explicit 16 or 32 char in 'x /s'
>
> >>>>> "Pierre" == Pierre Muller <pierre.muller@ics-cnrs.unistra.fr>
> writes:
>
> Pierre> But I don't know exactly for other languages and I would like
> Pierre> to be sure about what you want me to add to the docs...
>
> I think no other language has been updated to deal with wide
> characters.

At least pascal language was able to display
"simple" wide characters correctly (i.e. 16-bit strings with numeric values
in the 32-127 range)
before the patch that explicitly discarded the size modifier for /s.

> Pierre> Furthermore if you look into charset_for_string_type
> Pierre> function in c-lang.c source, you will see that there are two
> FIXME
> Pierre> just right at the position of these charset name settings.
>
> Yeah ... those are actually pedantic FIXMEs, in that (IIRC) nothing
> guarantees that char16_t==UTF-16, even though that is the common
> meaning.
>
> Pierre> To answer Tom's concern about the change in classify_type
> function,
> Pierre> I modified my patch to change the elttype in do_examine to
> match exactly
> Pierre> what is expected by charset_for_string_type function.
> Pierre> Thus this new version has no modification in c-lang.c file.
>
> Suppose the inferior does not define char16_t. Won't this new code
> allocate a new type each time the user uses x/hs? That seems bad.

Well, I supposed (wrongly) that the arch_type call would
make that newly defined type accessible to the next call to lookup_typename
but, after verification, it appears that you are right
and that the newly type is lost...
I don't know how we should handle this case, but I don't think that it is
the first time we use arch_type function inside GDB.
Should I add two new fields to builtin_type struct?
That is what I tried below.

> What about passing the desired encoding to LA_PRINT_STRING, via a new
> argument to val_print_string? That makes the patch a lot bigger,
> though
> it is mostly mechanical.
>
> Pierre> I also added a very basic check for string display using 'x
> Pierre> /hs' and 'x /ws'.
>
> Thanks.
>
> Pierre> + case 's':
> Pierre> + /* Display strings with byte size chars unless explicitly
> specified.
> Pierre> */
> Pierre> + val.size = 'b';
> Pierre> + break;
>
> I think x/hs followed by x should probably print another wide string.
> I couldn't tell offhand if it does this or not.

This is what I wrote in the documentation part of the patch,
the idea was to limit the behavior change as compared to previous versions
of GDB:
only 'x /hs' or 'x /ws' would display 16 or 32 bit strings,
any use without the explicit size specifier would fall back to implicit 'x
/bs'
this of course also would happen if you use 'x ' command without any
specifier
at all. It seems nevertheless that the patch I sent out finally
failed to do this properly. This new version seems to be closer to the
documentation I gave.

Here is a new version of the patch
using builtin_char16 and builtin_char32.

Pierre

2010-03-31 Pierre Muller <muller@ics.u-strasbg.fr>

* gdbtypes.h (builtin_type): Add BUILTIN_CHAR16 and BUILTIN_CHAR32
fields.
* gdbtypes.c (gdbtypes_post_init): Set BUILTIN_CHAR16 and
BUILTIN_CHAR32 fields.
* printcmd.c (decode_format): Set char size to '\0'
for strings unless explicit size is given.
(print_formatted): Correct calculation of NEXT_ADDRESS
for 16 or 32 bit strings.
(do_examine): Do not force byte size for strings.
Use builtin_char16 and builtin_char32 types to display
16 or 32 bit-wide strings.
(x_command): Set LAST_SIZE to 'b' for string type.

2010-03-31 Pierre Muller <muller@ics.u-strasbg.fr>

* gdb.texinfo (Examining memory): Update for
change in string display with explicit size.

2010-03-31 Pierre Muller <muller@ics.u-strasbg.fr>

* gdb.base/charset.c (Strin16, String32): New variables.
* gdb.base/charset.exp (gdb_test): Test correct display
of 16 or 32 bit strings.

Index: src/gdb/gdbtypes.h
===================================================================
RCS file: /cvs/src/src/gdb/gdbtypes.h,v
retrieving revision 1.125
diff -u -p -r1.125 gdbtypes.h
--- src/gdb/gdbtypes.h 15 Mar 2010 02:42:54 -0000 1.125
+++ src/gdb/gdbtypes.h 31 Mar 2010 12:57:26 -0000
@@ -1099,6 +1099,9 @@ struct builtin_type
struct type *builtin_int128;
struct type *builtin_uint128;

+ /* Multi-byte character types. */
+ struct type *builtin_char16;
+ struct type *builtin_char32;

/* Pointer types. */

Index: src/gdb/gdbtypes.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbtypes.c,v
retrieving revision 1.188
diff -u -p -r1.188 gdbtypes.c
--- src/gdb/gdbtypes.c 1 Mar 2010 17:19:22 -0000 1.188
+++ src/gdb/gdbtypes.c 31 Mar 2010 12:57:25 -0000
@@ -3474,6 +3474,13 @@ gdbtypes_post_init (struct gdbarch *gdba
TYPE_NOTTEXT (builtin_type->builtin_int8) = 1;
TYPE_NOTTEXT (builtin_type->builtin_uint8) = 1;

+ /* Multi-byte character types. */
+ builtin_type->builtin_char16
+ = arch_integer_type (gdbarch, 16, 0, "char16_t");
+ builtin_type->builtin_char32
+ = arch_integer_type (gdbarch, 32, 0, "char32_t");
+
+
/* Default data/code pointer types. */
builtin_type->builtin_data_ptr
= lookup_pointer_type (builtin_type->builtin_void);
Index: src/gdb/printcmd.c
===================================================================
RCS file: /cvs/src/src/gdb/printcmd.c,v
retrieving revision 1.173
diff -u -p -r1.173 printcmd.c
--- src/gdb/printcmd.c 5 Mar 2010 20:18:14 -0000 1.173
+++ src/gdb/printcmd.c 31 Mar 2010 15:20:22 -0000
@@ -260,6 +260,11 @@ decode_format (char **string_ptr, int of
/* Characters default to one byte. */
val.size = osize ? 'b' : osize;
break;
+ case 's':
+ /* Display strings with byte size chars unless explicitly specified.
*/
+ val.size = '\0';
+ break;
+
default:
/* The default is the size most recently specified. */
val.size = osize;
@@ -295,7 +300,7 @@ print_formatted (struct value *val, int
next_address = (value_address (val)
+ val_print_string (elttype,
value_address (val), -1,
- stream, options));
+ stream, options) * len);
}
return;

@@ -802,9 +807,11 @@ do_examine (struct format_data fmt, stru
next_gdbarch = gdbarch;
next_address = addr;

- /* String or instruction format implies fetch single bytes
- regardless of the specified size. */
- if (format == 's' || format == 'i')
+ /* Instruction format implies fetch single bytes
+ regardless of the specified size.
+ The case of strings is handled n decode_format, only explicit
+ size operator are not changed to 'b'. */
+ if (format == 'i')
size = 'b';

if (size == 'a')
@@ -831,6 +838,27 @@ do_examine (struct format_data fmt, stru
else if (size == 'g')
val_type = builtin_type (next_gdbarch)->builtin_int64;

+ if (format == 's')
+ {
+ struct type *char_type = NULL;
+ /* Search for "char16_t" or "char32_t" types or fall back to 8-bit
char
+ if type is not found. */
+ if (size == 'h')
+ char_type = builtin_type (next_gdbarch)->builtin_char16;
+ else if (size == 'w')
+ char_type = builtin_type (next_gdbarch)->builtin_char32;
+ if (char_type)
+ val_type = char_type;
+ else
+ {
+ if (size != '\0' && size != 'b')
+ warning (_("Unable to display strings with size '%c', using 'b'
\
+instead."), size);
+ size = 'b';
+ val_type = builtin_type (next_gdbarch)->builtin_int8;
+ }
+ }
+
maxelts = 8;
if (size == 'w')
maxelts = 4;
@@ -1412,8 +1440,11 @@ x_command (char *exp, int from_tty)
do_examine (fmt, next_gdbarch, next_address);

/* If the examine succeeds, we remember its size and format for next
- time. */
- last_size = fmt.size;
+ time. Set last_size to 'b' for strings. */
+ if (fmt.format == 's')
+ last_size = 'b'
+ else
+ last_size = fmt.size;
last_format = fmt.format;

/* Set a couple of internal variables if appropriate. */
Index: src/gdb/doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.680
diff -u -p -r1.680 gdb.texinfo
--- src/gdb/doc/gdb.texinfo 12 Mar 2010 19:15:52 -0000 1.680
+++ src/gdb/doc/gdb.texinfo 18 Mar 2010 20:43:12 -0000
@@ -7236,8 +7236,11 @@ Giant words (eight bytes).
@end table

Each time you specify a unit size with @code{x}, that size becomes the
-default unit the next time you use @code{x}. (For the @samp{s} and
-@samp{i} formats, the unit size is ignored and is normally not written.)
+default unit the next time you use @code{x}. For the @samp{i} format,
+the unit size is ignored and is normally not written. For the @samp{s}
format,
+the unit size defaults to @samp{b}, unless it is explicitly given.
+Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
+32-bit strings. The next use of @kbd{x /s} will again display 8-bit
strings.

@item @var{addr}, starting display address
@var{addr} is the address where you want @value{GDBN} to begin displaying
Index: src/gdb/testsuite/gdb.base/charset.c
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/charset.c,v
retrieving revision 1.12
diff -u -p -r1.12 charset.c
--- src/gdb/testsuite/gdb.base/charset.c 1 Jan 2010 07:32:00 -0000
1.12
+++ src/gdb/testsuite/gdb.base/charset.c 22 Mar 2010 22:25:34 -0000
@@ -65,6 +65,9 @@ typedef unsigned int char32_t;
char16_t uvar;
char32_t Uvar;

+char16_t *String16;
+char32_t *String32;
+
/* A typedef to a typedef should also work. */
typedef wchar_t my_wchar_t;
my_wchar_t myvar;
Index: src/gdb/testsuite/gdb.base/charset.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.base/charset.exp,v
retrieving revision 1.21
diff -u -p -r1.21 charset.exp
--- src/gdb/testsuite/gdb.base/charset.exp 17 Feb 2010 22:05:58 -0000
1.21
+++ src/gdb/testsuite/gdb.base/charset.exp 22 Mar 2010 22:25:35 -0000
@@ -616,4 +616,21 @@ gdb_test "print 'a' == 'a' || 'b' == 'b'
".* = 1" \
"EVAL_SKIP cleanup handling regression test"

+
+proc string_display { var_name set_prefix x_size x_type} {
+ gdb_test "set ${var_name} = ${set_prefix}\"Test String\\0with zeroes\""
"" "Assign ${var_name} with prefix ${set_prefix}"
+ gdb_test "x /2${x_size}s ${var_name}" ".* ${x_type}\"Test
String\"\[\r\n\]+.* ${x_type}\"with zeroes\"" "Display String ${var_name}
with x/${x_size}s"
+}
+
+string_display String16 u h u
+if {$wchar_size == 2} {
+ string_display String16 L h u
+}
+
+string_display String32 U w U
+if {$wchar_size == 4} {
+ string_display String32 L w U
+}
+
+
gdb_exit