Re: [RFC] Signed/unsigned character arrays are not strings

[Jan Kratochvil <jan.kratochvil@redhat.com>]

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Hi Eli,

On Thu, 25 Jan 2007 05:23:01 +0100, Eli Zaretskii wrote:
> > Date: Thu, 25 Jan 2007 02:54:22 +0100
> > From: Jan Kratochvil <jan.kratochvil@redhat.com>
> > 
> > currently all these types are printed as strings:
> > 	char
> > 	signed char
> > 	unsigned char
> > the patch will reduce the printed strings only to
> > 	char
> > and the signed/unsigned version gets printed as an array of byte values
> > (characters).  I hope nobody uses sign-specification for strings.
> 
> I must say I'm uneasy about this.  Signedness could be random.  What
> will happen on platforms where `char' is unsigned by default?

I had to find an answer to your interesting comment now myself:

# The string identification works despite the compiler flags below due to
# gdbtypes.c:
#   if (name && strcmp (name, "char") == 0)
#     TYPE_FLAGS (type) |= TYPE_FLAG_NOSIGN;

Provided there now an additional explicit testcase targeting your comment.


> Anyway, this change should probably be reflected in the manual, and
> perhaps also in NEWS.

Provided if it is satisfactionary.


> What bug? can you show it?

Originally posted by personal mail only, formally submitted before as:
	https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=224128


Attaching also "gdb-cvs-nosign-char.patch" for possible comments.
It starts printing
	$1 = {65 'A', 0 '\0'}
finally as
	$1 = {65, 0}
Not submitting it for commit review as it breaks the whole testsuite.
Still if anybody could update the testsuite it would be IMO a helpful patch.
Currently GDB displays the variants " 'X'" in many inappropriate cases.



Regards,
Lace

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2007-01-25  Jan Kratochvil <jan.kratochvil@redhat.com>

	* c-valprint.c (c_val_print): Require strings to be of no-signed CHARs.
	* NEWS: Describe CHAR array vs. string identifcation rules.

2007-01-25  Jan Kratochvil <jan.kratochvil@redhat.com>

	* gdb.texinfo: Describe CHAR array vs. string identifcation rules.

2007-01-25  Jan Kratochvil <jan.kratochvil@redhat.com>

	* gdb.base/charsign.exp, gdb.base/charsign.c: New files.
	* gdb.arch/i386-sse.exp: Check $xmm.v16_int8 printing as a number array.
	* gdb.base/printcmds.exp: Sign-provided CHARs now became arrays.
	* gdb.base/setvar.exp: Likewise.


--- gdb/NEWS	21 Jan 2007 17:48:53 -0000	1.211
+++ gdb/NEWS	25 Jan 2007 11:24:45 -0000
@@ -15,6 +15,9 @@ frequency signals (e.g. SIGALRM) via the
 target's overall architecture.  GDB can read a description from
 a local file or over the remote serial protocol.
 
+* Arrays of specifically SIGNED or UNSIGNED CHARs are now printed as arrays
+  of numbers.
+
 * New commands
 
 set mem inaccessible-by-default
--- gdb/c-valprint.c	9 Jan 2007 17:58:50 -0000	1.41
+++ gdb/c-valprint.c	25 Jan 2007 11:24:45 -0000
@@ -96,7 +96,7 @@ c_val_print (struct type *type, const gd
 	    }
 	  /* For an array of chars, print with string syntax.  */
 	  if (eltlen == 1 &&
-	      ((TYPE_CODE (elttype) == TYPE_CODE_INT)
+	      ((TYPE_CODE (elttype) == TYPE_CODE_INT && TYPE_NOSIGN (elttype))
 	       || ((current_language->la_language == language_m2)
 		   && (TYPE_CODE (elttype) == TYPE_CODE_CHAR)))
 	      && (format == 0 || format == 's'))
--- gdb/doc/ChangeLog	20 Jan 2007 16:51:56 -0000	1.635
+++ gdb/doc/ChangeLog	25 Jan 2007 11:24:48 -0000
@@ -1,3 +1,7 @@
+2007-01-25  Jan Kratochvil <jan.kratochvil@redhat.com>
+
+	gdb.texinfo: Describe CHAR array vs. string identifcation rules.
+
 2007-01-20  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>  (tiny change)
 
 	* agentexpr.texi: Fix typos.
--- gdb/doc/gdb.texinfo	20 Jan 2007 16:51:55 -0000	1.379
+++ gdb/doc/gdb.texinfo	25 Jan 2007 11:24:58 -0000
@@ -5632,6 +5632,26 @@ If you ask to print an object whose cont
 by the debug information, @value{GDBN} will say @samp{<incomplete
 type>}.  @xref{Symbols, incomplete type}, for more about this.
 
+Strings are identified as arrays of @code{char} values without specified
+signedness.  Arrays of either @code{signed char} or @code{unsigned char} get
+printed as arrays of 1 byte sized integers.  @code{-fsigned-char} or
+@code{-funsigned-char} @value{GCC} options have no effect as @value{GDBN}
+defines literal string type @code{"char"} as @code{char} without a sign.
+For program code
+
+@smallexample
+char var0[] = "A";
+signed char var1[] = "A";
+@end smallexample
+
+You get during debugging
+@smallexample
+(gdb) print var0
+$1 = "A"
+(gdb) print var1
+$2 = @{65 'A', 0 '\0'@}
+@end smallexample
+
 @node Arrays
 @section Artificial arrays
 
--- gdb/testsuite/gdb.arch/i386-sse.exp	9 Jan 2007 17:59:09 -0000	1.5
+++ gdb/testsuite/gdb.arch/i386-sse.exp	25 Jan 2007 11:24:58 -0000
@@ -83,7 +83,10 @@ gdb_continue_to_breakpoint "continue to 
 foreach r {0 1 2 3 4 5 6 7} {
     gdb_test "print \$xmm$r.v4_float" \
         ".. = \\{$r, $r.25, $r.5, $r.75\\}.*" \
-        "check contents of %xmm$r"
+        "check float contents of %xmm$r"
+    gdb_test "print \$xmm$r.v16_int8" \
+        ".. = \\{(-?\[0-9\]+ '.*', ){15}-?\[0-9\]+ '.*'\\}.*" \
+        "check int8 contents of %xmm$r"
 }
 
 foreach r {0 1 2 3 4 5 6 7} {
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb/testsuite/gdb.base/charsign.c	25 Jan 2007 11:24:58 -0000
@@ -0,0 +1,37 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2007 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+ 
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+   Please email any bugs, comments, and/or additions to this file to:
+   bug-gdb@prep.ai.mit.edu  */
+
+int main()
+{
+  return 0;
+}
+
+char n[]="A";
+signed char s[]="A";
+unsigned char u[]="A";
+
+typedef char char_n;
+typedef signed char char_s;
+typedef unsigned char char_u;
+
+char_n n_typed[]="A";
+char_s s_typed[]="A";
+char_u u_typed[]="A";
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb/testsuite/gdb.base/charsign.exp	25 Jan 2007 11:24:58 -0000
@@ -0,0 +1,70 @@
+# Copyright 2007 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+set prms_id 0
+set bug_id 0
+
+set testfile charsign
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+
+proc do_test { cflags } {
+    global srcdir
+    global binfile
+    global subdir
+    global srcfile
+    global gdb_prompt
+
+    if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable [list debug additional_flags=$cflags]] != "" } {
+	untested "Couldn't compile test program"
+	return -1
+    }
+
+    # Get things started.
+
+    gdb_exit
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load ${binfile}
+
+    # For C programs, "start" should stop in main().
+
+    gdb_test "p n" \
+	     "= \"A\""
+    gdb_test "p s" \
+	     "= \\{65 'A', 0 '\\\\0'\\}"
+    gdb_test "p u" \
+	     "= \\{65 'A', 0 '\\\\0'\\}"
+    gdb_test "p n_typed" \
+	     "= \"A\""
+    gdb_test "p s_typed" \
+	     "= \\{65 'A', 0 '\\\\0'\\}"
+    gdb_test "p u_typed" \
+	     "= \\{65 'A', 0 '\\\\0'\\}"
+}
+
+# The string identification works despite the compiler flags below due to
+# gdbtypes.c:
+#   if (name && strcmp (name, "char") == 0)
+#     TYPE_FLAGS (type) |= TYPE_FLAG_NOSIGN;
+
+do_test {}
+do_test {-fsigned-char}
+do_test {-funsigned-char}
--- gdb/testsuite/gdb.base/printcmds.exp	9 Jan 2007 17:59:11 -0000	1.14
+++ gdb/testsuite/gdb.base/printcmds.exp	25 Jan 2007 11:24:58 -0000
@@ -590,18 +590,18 @@ proc test_print_char_arrays {} {
     gdb_test "set print address on" ""
 
     gdb_test "p arrays" \
-	" = {array1 = \"abc\", array2 = \"d\", array3 = \"e\", array4 = \"fg\", array5 = \"hij\"}"
+	" = \\{array1 = \\{97 'a', 98 'b', 99 'c', 0 '\\\\0'\\}, array2 = \\{100 'd'\\}, array3 = \\{101 'e'\\}, array4 = \\{102 'f', 103 'g'\\}, array5 = \\{104 'h', 105 'i', 106 'j', 0 '\\\\0'\\}\\}"
 
     gdb_test "p parrays"		" = \\(struct some_arrays \\*\\) $hex"
-    gdb_test "p parrays->array1"	" = \"abc\""
+    gdb_test "p parrays->array1"	" = \\{97 'a', 98 'b', 99 'c', 0 '\\\\0'\\}"
     gdb_test "p &parrays->array1"	" = \\(unsigned char \\(\\*\\)\\\[4\\\]\\) $hex"
-    gdb_test "p parrays->array2"	" = \"d\""
+    gdb_test "p parrays->array2"	" = \\{100 'd'\\}"
     gdb_test "p &parrays->array2"	" = \\(unsigned char \\(\\*\\)\\\[1\\\]\\) $hex"
-    gdb_test "p parrays->array3"	" = \"e\""
+    gdb_test "p parrays->array3"	" = \\{101 'e'\\}"
     gdb_test "p &parrays->array3"	" = \\(unsigned char \\(\\*\\)\\\[1\\\]\\) $hex"
-    gdb_test "p parrays->array4"	" = \"fg\""
+    gdb_test "p parrays->array4"	" = \\{102 'f', 103 'g'\\}"
     gdb_test "p &parrays->array4"	" = \\(unsigned char \\(\\*\\)\\\[2\\\]\\) $hex"
-    gdb_test "p parrays->array5"	" = \"hij\""
+    gdb_test "p parrays->array5"	" = \\{104 'h', 105 'i', 106 'j', 0 '\\\\0'\\}"
     gdb_test "p &parrays->array5"	" = \\(unsigned char \\(\\*\\)\\\[4\\\]\\) $hex"
 
     gdb_test "set print address off" ""
--- gdb/testsuite/gdb.base/setvar.exp	9 Jan 2007 17:59:11 -0000	1.10
+++ gdb/testsuite/gdb.base/setvar.exp	25 Jan 2007 11:24:58 -0000
@@ -233,11 +233,11 @@ test_set "set variable v_char_array\[0\]
 #
 # test "set variable" for "signed char array[2]"
 #
-test_set "set variable v_signed_char_array\[0\]='h'" "set variable v_signed_char_array\[1\]='i'" "print v_signed_char_array" ".*.\[0-9\]* =.*\"hi\""        "set variable signed char array=\"hi\" (string)" 
+test_set "set variable v_signed_char_array\[0\]='h'" "set variable v_signed_char_array\[1\]='i'" "print v_signed_char_array" ".*.\[0-9\]* =.*\\{104 'h', 105 'i'\\}"        "set variable signed char array=\"hi\" (string)" 
 #
 # test "set variable" for "unsigned char array[2]"
 #
-test_set "set variable v_unsigned_char_array\[0\]='h'" "set variable v_unsigned_char_array\[1\]='i'" "print v_unsigned_char_array" ".*.\[0-9\]* =.*\"hi\""        "set variable unsigned char array=\"hi\" (string)" 
+test_set "set variable v_unsigned_char_array\[0\]='h'" "set variable v_unsigned_char_array\[1\]='i'" "print v_unsigned_char_array" ".*.\[0-9\]* =.*\\{104 'h', 105 'i'\\}"        "set variable unsigned char array=\"hi\" (string)" 
 #
 # test "set variable" for "short array[2]"
 #
@@ -289,11 +289,11 @@ test_set "set v_char_pointer=v_char_arra
 #
 # test "set variable" for type "signed char *"
 #
-test_set "set v_signed_char_pointer=v_signed_char_array" "set variable *(v_signed_char_pointer)='h'" "set variable *(v_signed_char_pointer+1)='i'" "print v_signed_char_array" ".*.\[0-9\]* =.*\"hi\""  "print *(v_signed_char_pointer+1)" ".*.\[0-9\]* = 105 \'i\'"     "set variable signed char pointer=\"hi\" (string)" 
+test_set "set v_signed_char_pointer=v_signed_char_array" "set variable *(v_signed_char_pointer)='h'" "set variable *(v_signed_char_pointer+1)='i'" "print v_signed_char_array" ".*.\[0-9\]* =.*\\{104 'h', 105 'i'\\}"  "print *(v_signed_char_pointer+1)" ".*.\[0-9\]* = 105 \'i\'"     "set variable signed char pointer=\"hi\" (string)" 
 #
 # test "set variable" for type "unsigned char *"
 #
-test_set "set v_unsigned_char_pointer=v_unsigned_char_array" "set variable *(v_unsigned_char_pointer)='h'" "set variable *(v_unsigned_char_pointer+1)='i'" "print v_unsigned_char_array" ".*.\[0-9\]* =.*\"hi\""  "print *(v_unsigned_char_pointer+1)" ".*.\[0-9\]* = 105 \'i\'"     "set variable unsigned char pointer=\"hi\" (string)" 
+test_set "set v_unsigned_char_pointer=v_unsigned_char_array" "set variable *(v_unsigned_char_pointer)='h'" "set variable *(v_unsigned_char_pointer+1)='i'" "print v_unsigned_char_array" ".*.\[0-9\]* =.*\\{104 'h', 105 'i'\\}"  "print *(v_unsigned_char_pointer+1)" ".*.\[0-9\]* = 105 \'i\'"     "set variable unsigned char pointer=\"hi\" (string)" 
 #
 # test "set variable" for type "short *"
 #

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--- gdb/c-valprint.c	9 Jan 2007 17:58:50 -0000	1.41
+++ gdb/c-valprint.c	24 Jan 2007 22:14:49 -0000
@@ -398,7 +398,7 @@ c_val_print (struct type *type, const gd
 	     Since we don't know whether the value is really intended to
 	     be used as an integer or a character, print the character
 	     equivalent as well. */
-	  if (TYPE_LENGTH (type) == 1)
+	  if (TYPE_LENGTH (type) == 1 && TYPE_NOSIGN (elttype))
 	    {
 	      fputs_filtered (" ", stream);
 	      LA_PRINT_CHAR ((unsigned char) unpack_long (type, valaddr + embedded_offset),