Re: [RFA] Add la_getstr member to language_defn

Thiago Jung Bauermann
2008-11-24T01:41:53Z

Hi Daniel,

Thanks for your review.

Am Sonntag, den 23.11.2008, 11:10 -0500 schrieb Daniel Jacobowitz:
> On Sun, Nov 23, 2008 at 03:14:37AM -0200, Thiago Jung Bauermann wrote:
> > One improvement which is easy to make but I left for later (this patch
> > is big enough already) is to nuke target_read_string and make its
> > callers use read_string instead (the former implements just a subset of
> > what the latter provides). It would be a simple modification, but would
> > affect code specific to targets to which I don't have access to
> > (target_read_string is almost exclusively used in solib-*.c). I can work
> > on a subsequent patch to do that if you think it's safe enough to not
> > require my testing on all affected targets.
>
> What's the difference between them?

target_read_string assumes 1-byte characters, so it is equivalent to
calling read_string with a character width of 1.

Also, the way they fetch the string differs (I don't know how relevant
is the difference): target_read_string reads in steps of at most 4
bytes, and doubles its allocated buffer each time it gets full, while
read_string reads the whole string at once if its size is known, or else
reads in steps of at most 8 bytes, and linearly increases its allocated
buffer in steps of 8 bytes.

I mentioned substituting one for the other because I tend to dislike
having two implementations of basically the same thing.

> > +/* Obtain a C string from the inferior, storing it in a newly allocated
> > + buffer in BUFFER, which should be freed by the caller. If VALUE is an
> > + array with known length, the function will copy all of its contents to
> > + the buffer. If the length is not known, read until a null byte is found.
> > + LENGTH will contain the size of the string (not counting the NULL
> > + character).
>
> This is the right behavior for gdb's "print VAR". But I'm not sure
> it's the right behavior for a method named la_getstr - in fact I think
> it isn't.

The comment is wrong. c_getstr actually reads until a null character is
found, but doesn't read past the end of an array with known length. I
updated the comment to reflect that.

Except that there was a bug for GDB-hosted strings, in which case the
function behaved as described by the comment. I fixed it now.

> If I ask for the contents of the array, I should get sixteen bytes.
> But if I ask for a string I ought to get, in my opinion, up to sixteen
> bytes. Characters up to but not including the first zero, or sixteen
> at most. A ps implementation which prints "comm\0er command" is not
> very helpful :-)

Agreed, and that's what I (mostly) implemented, but got confused by the
GDB-hosted special case. Thanks for the detailed example anyway.

By the way, the special case is for not_lval and lval_internalvar.
Should I test for lval_internalvar_component as well?

> BTW, it's not a NULL character; it's NUL, the null character. NULL
> in uppercase is the pointer.

Fixed comments.

What about this version?
--
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center

2008-11-23 Thiago Jung Bauermann <bauerman@br.ibm.com>

* language.h (language_dfn): Add la_getstr member.
(LA_GET_STRING): New macro.
(default_getstr): New prototype.
* language.c (default_getstr): New function.
(unknown_language_defn, auto_language_defn, local_language_defn): Use
default_getstr for la_getstr.
* c-lang.c (c_getstr): New function.
(c_language_defn, cplus_language_defn, asm_language_defn): Use
c_getstr for la_getstr.
(minimal_language_defn): Use default_getstr for la_getstr.
* ada-lang.c (ada_language_defn): Likewise.
* f-lang.c (f_language_defn): Likewise.
* jv-lang.c (java_language_defn): Likewise.
* m2-lang.c (m2_language_defn): Likewise.
* objc-lang.c (objc_language_defn): Likewise.
* p-lang.c (p_language_defn): Likewise.
* scm-lang.c (scm_language_defn): Likewise.
* typeprint.c (type_to_string): New function.
* value.h (type_to_string): New prototype.
* valprint.c (val_print_string): Factor out code for reading string
from the inferior into its own function. Put 2 spaces after period
in comments.
(read_string): New function.
* valprint.h (read_string): New prototype.

Index: gdb.git/gdb/ada-lang.c
===================================================================
--- gdb.git.orig/gdb/ada-lang.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/ada-lang.c 2008-11-23 23:13:59.000000000 -0200
@@ -11084,6 +11084,7 @@ const struct language_defn ada_language_
ada_language_arch_info,
ada_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

Index: gdb.git/gdb/c-lang.c
===================================================================
--- gdb.git.orig/gdb/c-lang.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/c-lang.c 2008-11-23 23:14:04.000000000 -0200
@@ -181,6 +181,113 @@ c_printstr (struct ui_file *stream, cons
if (force_ellipses || i < length)
fputs_filtered ("...", stream);
}
+
+/* Obtain a C string from the inferior storing it in a newly allocated
+ buffer in BUFFER, which should be freed by the caller. The string is
+ read until a null character is found. If VALUE is an array with known
+ length, the function will not read past the end of the array. LENGTH
+ will contain the size of the string in bytes (not counting the null
+ character).
+
+ Assumes strings are terminated by a null character. The size of a character
+ is determined by the length of the target type of the pointer or array.
+ This means that a null byte present in a multi-byte character will not
+ terminate the string unless the whole character is null.
+
+ Unless an exception is thrown, BUFFER will always be allocated, even on
+ failure. In this case, some characters might have been read before the
+ failure happened. Check LENGTH to recognize this situation.
+
+ Return 0 on success, errno on failure. */
+
+static int
+c_getstr (struct value *value, gdb_byte **buffer, int *length)
+{
+ int fetchlimit, err, width;
+ struct type *type = value_type (value);
+ struct type *element_type = TYPE_TARGET_TYPE (type);
+
+ if (element_type == NULL)
+ goto error;
+
+ if (TYPE_CODE (type) == TYPE_CODE_ARRAY)
+ {
+ /* If we know the size of the array, we can use it as a limit on the
+ number of characters to be fetched. */
+ if ((TYPE_NFIELDS (type) == 1)
+ && TYPE_CODE (TYPE_FIELD_TYPE (type, 0)) == TYPE_CODE_RANGE)
+ {
+ LONGEST low_bound, high_bound;
+
+ get_discrete_bounds (TYPE_FIELD_TYPE (type, 0),
+ &low_bound, &high_bound);
+ fetchlimit = high_bound - low_bound + 1;
+ }
+ else
+ fetchlimit = -1;
+ }
+ else if (TYPE_CODE (value_type (value)) == TYPE_CODE_PTR)
+ fetchlimit = -1;
+ else
+ /* We work only with arrays and pointers. */
+ goto error;
+
+ element_type = check_typedef (element_type);
+ if ((TYPE_CODE (element_type) != TYPE_CODE_INT)
+ && (TYPE_CODE (element_type) != TYPE_CODE_CHAR))
+ /* If the elements are not integers or characters, we don't consider it
+ a string. */
+ goto error;
+
+ width = TYPE_LENGTH (element_type);
+
+ /* If the string lives in GDB's memory intead of the inferior's, then we
+ just need to copy it to BUFFER. Also, since such strings are arrays
+ with known size, FETCHLIMIT will hold the size of the array. */
+ if (((VALUE_LVAL (value) == not_lval)
+ || (VALUE_LVAL (value) == lval_internalvar)) && (fetchlimit != -1))
+ {
+ int i;
+ const gdb_byte *contents = value_contents (value);
+
+ /* Look for a null character. */
+ for (i = 0; i < fetchlimit; i++)
+ if (extract_unsigned_integer (contents + i*width, width) == 0)
+ break;
+
+ /* i is now either the number of non-null characters, or fetchlimit. */
+ *length = i*width;
+ *buffer = xmalloc (*length);
+ memcpy (*buffer, contents, *length);
+ err = 0;
+ }
+ else
+ err = read_string (value_as_address (value), -1, width, fetchlimit,
+ buffer, length);
+
+ /* If the last character is null, subtract it from length. */
+ if (extract_unsigned_integer (*buffer + *length - width, width) == 0)
+ *length -= width;
+
+ return err;
+
+error:
+ {
+ char *type_str;
+ struct cleanup *old_chain;
+
+ type_str = type_to_string (type);
+ if (type_str)
+ {
+ old_chain = make_cleanup (xfree, type_str);
+ error (_("Trying to read string with inappropriate type `%s'."),
+ type_str);
+ }
+ else
+ error (_("Trying to read string with inappropriate type."));
+ }
+}
+
\f
/* Preprocessing and parsing C and C++ expressions. */

@@ -419,6 +526,7 @@ const struct language_defn c_language_de
c_language_arch_info,
default_print_array_index,
default_pass_by_reference,
+ c_getstr,
LANG_MAGIC
};

@@ -537,6 +645,7 @@ const struct language_defn cplus_languag
cplus_language_arch_info,
default_print_array_index,
cp_pass_by_reference,
+ c_getstr,
LANG_MAGIC
};

@@ -574,6 +683,7 @@ const struct language_defn asm_language_
c_language_arch_info, /* FIXME: la_language_arch_info. */
default_print_array_index,
default_pass_by_reference,
+ c_getstr,
LANG_MAGIC
};

@@ -616,6 +726,7 @@ const struct language_defn minimal_langu
c_language_arch_info,
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

Index: gdb.git/gdb/f-lang.c
===================================================================
--- gdb.git.orig/gdb/f-lang.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/f-lang.c 2008-11-23 23:13:59.000000000 -0200
@@ -343,6 +343,7 @@ const struct language_defn f_language_de
f_language_arch_info,
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

Index: gdb.git/gdb/jv-lang.c
===================================================================
--- gdb.git.orig/gdb/jv-lang.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/jv-lang.c 2008-11-23 23:13:59.000000000 -0200
@@ -1128,6 +1128,7 @@ const struct language_defn java_language
java_language_arch_info,
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

Index: gdb.git/gdb/language.c
===================================================================
--- gdb.git.orig/gdb/language.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/language.c 2008-11-23 23:13:59.000000000 -0200
@@ -1043,6 +1043,12 @@ default_print_array_index (struct value
fprintf_filtered (stream, "] = ");
}

+int
+default_getstr (struct value *value, gdb_byte **buffer, int *length)
+{
+ error (_("Getting a string is unsupported in this language."));
+}
+
/* Define the language that is no language. */

static int
@@ -1165,6 +1171,7 @@ const struct language_defn unknown_langu
unknown_language_arch_info, /* la_language_arch_info. */
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

@@ -1203,6 +1210,7 @@ const struct language_defn auto_language
unknown_language_arch_info, /* la_language_arch_info. */
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

@@ -1240,6 +1248,7 @@ const struct language_defn local_languag
unknown_language_arch_info, /* la_language_arch_info. */
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};
\f
Index: gdb.git/gdb/language.h
===================================================================
--- gdb.git.orig/gdb/language.h 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/language.h 2008-11-23 23:13:59.000000000 -0200
@@ -282,6 +282,12 @@ struct language_defn
reference at the language level. */
int (*la_pass_by_reference) (struct type *type);

+ /* Obtain a string from the inferior, storing it in a newly allocated
+ buffer in BUFFER, which should be freed by the caller. LENGTH will
+ hold the size in bytes of the string (only actual characters, excluding
+ an eventual terminating null character). */
+ int (*la_getstr) (struct value *value, gdb_byte **buffer, int *length);
+
/* Add fields above this point, so the magic number is always last. */
/* Magic number for compat checking */

@@ -380,6 +386,8 @@ extern enum language set_language (enum
force_ellipses,options))
#define LA_EMIT_CHAR(ch, stream, quoter) \
(current_language->la_emitchar(ch, stream, quoter))
+#define LA_GET_STRING(value, buffer, length) \
+ (current_language->la_getstr(value, buffer, length))

#define LA_PRINT_ARRAY_INDEX(index_value, stream, optins) \
(current_language->la_print_array_index(index_value, stream, options))
@@ -489,4 +497,6 @@ int default_pass_by_reference (struct ty
void default_print_typedef (struct type *type, struct symbol *new_symbol,
struct ui_file *stream);

+int default_getstr (struct value *value, gdb_byte **buffer, int *length);
+
#endif /* defined (LANGUAGE_H) */
Index: gdb.git/gdb/m2-lang.c
===================================================================
--- gdb.git.orig/gdb/m2-lang.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/m2-lang.c 2008-11-23 23:13:59.000000000 -0200
@@ -394,6 +394,7 @@ const struct language_defn m2_language_d
m2_language_arch_info,
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

Index: gdb.git/gdb/objc-lang.c
===================================================================
--- gdb.git.orig/gdb/objc-lang.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/objc-lang.c 2008-11-23 23:13:59.000000000 -0200
@@ -531,6 +531,7 @@ const struct language_defn objc_language
c_language_arch_info,
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

Index: gdb.git/gdb/p-lang.c
===================================================================
--- gdb.git.orig/gdb/p-lang.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/p-lang.c 2008-11-23 23:13:59.000000000 -0200
@@ -433,6 +433,7 @@ const struct language_defn pascal_langua
pascal_language_arch_info,
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

Index: gdb.git/gdb/scm-lang.c
===================================================================
--- gdb.git.orig/gdb/scm-lang.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/scm-lang.c 2008-11-23 23:13:59.000000000 -0200
@@ -273,6 +273,7 @@ const struct language_defn scm_language_
c_language_arch_info,
default_print_array_index,
default_pass_by_reference,
+ default_getstr,
LANG_MAGIC
};

Index: gdb.git/gdb/typeprint.c
===================================================================
--- gdb.git.orig/gdb/typeprint.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/typeprint.c 2008-11-23 23:13:59.000000000 -0200
@@ -33,6 +33,7 @@
#include "cp-abi.h"
#include "typeprint.h"
#include "gdb_string.h"
+#include "exceptions.h"
#include "valprint.h"
#include <errno.h>

@@ -78,6 +79,34 @@ type_print (struct type *type, char *var
LA_PRINT_TYPE (type, varstring, stream, show, 0);
}

+/* Print TYPE to a string, returning it. The caller is responsible for
+ freeing the string. */
+
+char *
+type_to_string (struct type *type)
+{
+ char *s = NULL;
+ long dummy;
+ struct ui_file *stb;
+ struct cleanup *old_chain;
+ volatile struct gdb_exception except;
+
+ stb = mem_fileopen ();
+ old_chain = make_cleanup_ui_file_delete (stb);
+
+ TRY_CATCH (except, RETURN_MASK_ALL)
+ {
+ type_print (type, "", stb, -1);
+ s = ui_file_xstrdup (stb, &dummy);
+ }
+ if (except.reason < 0)
+ s = NULL;
+
+ do_cleanups (old_chain);
+
+ return s;
+}
+
/* Print type of EXP, or last thing in value history if EXP == NULL.
show is passed to type_print. */

Index: gdb.git/gdb/valprint.c
===================================================================
--- gdb.git.orig/gdb/valprint.c 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/valprint.c 2008-11-23 23:37:25.000000000 -0200
@@ -1177,43 +1177,44 @@ partial_memory_read (CORE_ADDR memaddr,
return (nread);
}

-/* Print a string from the inferior, starting at ADDR and printing up to LEN
- characters, of WIDTH bytes a piece, to STREAM. If LEN is -1, printing
- stops at the first null byte, otherwise printing proceeds (including null
- bytes) until either print_max or LEN characters have been printed,
- whichever is smaller. */
-
-/* FIXME: Use target_read_string. */
+/* Read a string from the inferior, at ADDR, with LEN characters of WIDTH bytes
+ each. Fetch at most FETCHLIMIT characters. BUFFER will be set to a newly
+ allocated buffer containing the string, which the caller is responsible to
+ free, and BYTES_READ will be set to the number of bytes read. Returns 0 on
+ success, or errno on failure.
+
+ If LEN is -1, stops at the first null character (not necessarily the first
+ null byte) up to a maximum of FETCHLIMIT characters, otherwise reading
+ proceeds (including null characters) until LEN characters have been read.
+ Set FETCHLIMIT to UINT_MAX to read as many characters as possible from the
+ string.
+
+ Unless an exception is thrown, BUFFER will always be allocated, even on
+ failure. In this case, some characters might have been read before the
+ failure happened. Check BYTES_READ to recognize this situation.
+
+ Note: There was a FIXME asking to make this code use target_read_string,
+ but this function is more general (can read past null characters, up to
+ given LEN). Besides, it is used much more often than target_read_string
+ so it is more tested. Perhaps callers of target_read_string should use
+ this function instead? */

int
-val_print_string (CORE_ADDR addr, int len, int width, struct ui_file *stream,
- const struct value_print_options *options)
+read_string (CORE_ADDR addr, int len, int width, unsigned int fetchlimit,
+ gdb_byte **buffer, int *bytes_read)
{
- int force_ellipsis = 0; /* Force ellipsis to be printed if nonzero. */
- int errcode; /* Errno returned from bad reads. */
- unsigned int fetchlimit; /* Maximum number of chars to print. */
- unsigned int nfetch; /* Chars to fetch / chars fetched. */
- unsigned int chunksize; /* Size of each fetch, in chars. */
- gdb_byte *buffer = NULL; /* Dynamically growable fetch buffer. */
- gdb_byte *bufptr; /* Pointer to next available byte in buffer. */
- gdb_byte *limit; /* First location past end of fetch buffer. */
- struct cleanup *old_chain = NULL; /* Top of the old cleanup chain. */
- int found_nul; /* Non-zero if we found the nul char */
+ int found_nul; /* Non-zero if we found the nul char. */
+ int errcode; /* Errno returned from bad reads. */
+ unsigned int nfetch; /* Chars to fetch / chars fetched. */
+ unsigned int chunksize; /* Size of each fetch, in chars. */
+ gdb_byte *bufptr; /* Pointer to next available byte in buffer. */
+ gdb_byte *limit; /* First location past end of fetch buffer. */
+ struct cleanup *old_chain = NULL; /* Top of the old cleanup chain. */

- /* First we need to figure out the limit on the number of characters we are
- going to attempt to fetch and print. This is actually pretty simple. If
- LEN >= zero, then the limit is the minimum of LEN and print_max. If
- LEN is -1, then the limit is print_max. This is true regardless of
- whether print_max is zero, UINT_MAX (unlimited), or something in between,
- because finding the null byte (or available memory) is what actually
- limits the fetch. */
-
- fetchlimit = (len == -1 ? options->print_max : min (len, options->print_max));
-
- /* Now decide how large of chunks to try to read in one operation. This
+ /* Decide how large of chunks to try to read in one operation. This
is also pretty simple. If LEN >= zero, then we want fetchlimit chars,
so we might as well read them all in one operation. If LEN is -1, we
- are looking for a null terminator to end the fetching, so we might as
+ are looking for a NUL terminator to end the fetching, so we might as
well read in blocks that are large enough to be efficient, but not so
large as to be slow if fetchlimit happens to be large. So we choose the
minimum of 8 and fetchlimit. We used to use 200 instead of 8 but
@@ -1221,17 +1222,17 @@ val_print_string (CORE_ADDR addr, int le

chunksize = (len == -1 ? min (8, fetchlimit) : fetchlimit);

- /* Loop until we either have all the characters to print, or we encounter
- some error, such as bumping into the end of the address space. */
+ /* Loop until we either have all the characters, or we encounter
+ some error, such as bumping into the end of the address space. */

found_nul = 0;
old_chain = make_cleanup (null_cleanup, 0);

if (len > 0)
{
- buffer = (gdb_byte *) xmalloc (len * width);
- bufptr = buffer;
- old_chain = make_cleanup (xfree, buffer);
+ *buffer = (gdb_byte *) xmalloc (len * width);
+ bufptr = *buffer;
+ old_chain = make_cleanup (xfree, *buffer);

nfetch = partial_memory_read (addr, bufptr, len * width, &errcode)
/ width;
@@ -1241,32 +1242,36 @@ val_print_string (CORE_ADDR addr, int le
else if (len == -1)
{
unsigned long bufsize = 0;
+
+ *buffer = NULL;
+
do
{
QUIT;
nfetch = min (chunksize, fetchlimit - bufsize);

- if (buffer == NULL)
- buffer = (gdb_byte *) xmalloc (nfetch * width);
+ if (*buffer == NULL)
+ *buffer = (gdb_byte *) xmalloc (nfetch * width);
else
{
discard_cleanups (old_chain);
- buffer = (gdb_byte *) xrealloc (buffer, (nfetch + bufsize) * width);
+ *buffer = (gdb_byte *) xrealloc (*buffer,
+ (nfetch + bufsize) * width);
}

- old_chain = make_cleanup (xfree, buffer);
- bufptr = buffer + bufsize * width;
+ old_chain = make_cleanup (xfree, *buffer);
+ bufptr = *buffer + bufsize * width;
bufsize += nfetch;

- /* Read as much as we can. */
+ /* Read as much as we can. */
nfetch = partial_memory_read (addr, bufptr, nfetch * width, &errcode)
- / width;
+ / width;

- /* Scan this chunk for the null byte that terminates the string
+ /* Scan this chunk for the null character that terminates the string
to print. If found, we don't need to fetch any more. Note
that bufptr is explicitly left pointing at the next character
- after the null byte, or at the next character after the end of
- the buffer. */
+ after the null character, or at the next character after the end
+ of the buffer. */

limit = bufptr + nfetch * width;
while (bufptr < limit)
@@ -1279,7 +1284,7 @@ val_print_string (CORE_ADDR addr, int le
if (c == 0)
{
/* We don't care about any error which happened after
- the NULL terminator. */
+ the NUL terminator. */
errcode = 0;
found_nul = 1;
break;
@@ -1287,26 +1292,70 @@ val_print_string (CORE_ADDR addr, int le
}
}
while (errcode == 0 /* no error */
- && bufptr - buffer < fetchlimit * width /* no overrun */
- && !found_nul); /* haven't found nul yet */
+ && bufptr - *buffer < fetchlimit * width /* no overrun */
+ && !found_nul); /* haven't found NUL yet */
}
else
- { /* length of string is really 0! */
- buffer = bufptr = NULL;
+ { /* Length of string is really 0! */
+ *buffer = bufptr = NULL;
errcode = 0;
}

/* bufptr and addr now point immediately beyond the last byte which we
consider part of the string (including a '\0' which ends the string). */
+ *bytes_read = bufptr - *buffer;
+
+ QUIT;
+
+ discard_cleanups (old_chain);
+
+ return errcode;
+}
+
+/* Print a string from the inferior, starting at ADDR and printing up to LEN
+ characters, of WIDTH bytes a piece, to STREAM. If LEN is -1, printing
+ stops at the first null byte, otherwise printing proceeds (including null
+ bytes) until either print_max or LEN characters have been printed,
+ whichever is smaller. */
+
+int
+val_print_string (CORE_ADDR addr, int len, int width, struct ui_file *stream,
+ const struct value_print_options *options)
+{
+ int force_ellipsis = 0; /* Force ellipsis to be printed if nonzero. */
+ int errcode; /* Errno returned from bad reads. */
+ int found_nul; /* Non-zero if we found the nul char */
+ unsigned int fetchlimit; /* Maximum number of chars to print. */
+ int bytes_read;
+ gdb_byte *buffer = NULL; /* Dynamically growable fetch buffer. */
+ struct cleanup *old_chain = NULL; /* Top of the old cleanup chain. */
+
+ /* First we need to figure out the limit on the number of characters we are
+ going to attempt to fetch and print. This is actually pretty simple. If
+ LEN >= zero, then the limit is the minimum of LEN and print_max. If
+ LEN is -1, then the limit is print_max. This is true regardless of
+ whether print_max is zero, UINT_MAX (unlimited), or something in between,
+ because finding the null byte (or available memory) is what actually
+ limits the fetch. */
+
+ fetchlimit = (len == -1 ? options->print_max : min (len, options->print_max));
+
+ errcode = read_string (addr, len, width, fetchlimit, &buffer, &bytes_read);
+ old_chain = make_cleanup (xfree, buffer);
+
+ addr += bytes_read;

/* We now have either successfully filled the buffer to fetchlimit, or
- terminated early due to an error or finding a null char when LEN is -1. */
+ terminated early due to an error or finding a null char when LEN is -1. */
+
+ /* Determine found_nul by looking at the last character read. */
+ found_nul = extract_unsigned_integer (buffer + bytes_read - width, width) == 0;

if (len == -1 && !found_nul)
{
gdb_byte *peekbuf;

- /* We didn't find a null terminator we were looking for. Attempt
+ /* We didn't find a NUL terminator we were looking for. Attempt
to peek at the next character. If not successful, or it is not
a null byte, then force ellipsis to be printed. */

@@ -1316,26 +1365,24 @@ val_print_string (CORE_ADDR addr, int le
&& extract_unsigned_integer (peekbuf, width) != 0)
force_ellipsis = 1;
}
- else if ((len >= 0 && errcode != 0) || (len > (bufptr - buffer) / width))
+ else if ((len >= 0 && errcode != 0) || (len > bytes_read / width))
{
/* Getting an error when we have a requested length, or fetching less
than the number of characters actually requested, always make us
- print ellipsis. */
+ print ellipsis. */
force_ellipsis = 1;
}

- QUIT;
-
/* If we get an error before fetching anything, don't print a string.
But if we fetch something and then get an error, print the string
and then the error message. */
- if (errcode == 0 || bufptr > buffer)
+ if (errcode == 0 || bytes_read > 0)
{
if (options->addressprint)
{
fputs_filtered (" ", stream);
}
- LA_PRINT_STRING (stream, buffer, (bufptr - buffer) / width, width, force_ellipsis, options);
+ LA_PRINT_STRING (stream, buffer, bytes_read / width, width, force_ellipsis, options);
}

if (errcode != 0)
@@ -1353,9 +1400,11 @@ val_print_string (CORE_ADDR addr, int le
fprintf_filtered (stream, ": %s>", safe_strerror (errcode));
}
}
+
gdb_flush (stream);
do_cleanups (old_chain);
- return ((bufptr - buffer) / width);
+
+ return (bytes_read / width);
}
\f

Index: gdb.git/gdb/valprint.h
===================================================================
--- gdb.git.orig/gdb/valprint.h 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/valprint.h 2008-11-23 23:13:59.000000000 -0200
@@ -136,4 +136,7 @@ extern void print_hex_chars (struct ui_f

extern void print_char_chars (struct ui_file *, const gdb_byte *,
unsigned int, enum bfd_endian);
+
+int read_string (CORE_ADDR addr, int len, int width, unsigned int fetchlimit,
+ gdb_byte **buffer, int *bytes_read);
#endif
Index: gdb.git/gdb/value.h
===================================================================
--- gdb.git.orig/gdb/value.h 2008-11-23 22:51:43.000000000 -0200
+++ gdb.git/gdb/value.h 2008-11-23 23:13:59.000000000 -0200
@@ -514,6 +514,8 @@ extern void modify_field (gdb_byte *addr
extern void type_print (struct type *type, char *varstring,
struct ui_file *stream, int show);

+extern char * type_to_string (struct type *type);
+
extern gdb_byte *baseclass_addr (struct type *type, int index,
gdb_byte *valaddr,
struct value **valuep, int *errp);