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Re: [python][patch] Add options length parameter to value.string(...)
Thiago Jung Bauermann wrote:
I looked at the patch and it seems good. I have just a few nits, I hope
you will put up with me just a tad bit more. :-)
Thanks for the swift review.
static PyObject *
valpy_string (PyObject *self, PyObject *args, PyObject *kw)
{
This function has the following comment above it:
/* Implementation of gdb.Value.string ([encoding] [, errors]) -> string
Return Unicode string with value contents. If ENCODING is not given,
the string is assumed to be encoded in the target's charset. */
Would you mind adding "[, length] to the prototype?
Ack, sorry. Added.
+ gdb_test "python print st.string (length = 0)" "" "Test string (length = 0) is empty"
Does using "" as test pattern really test for an empty line? I know that
gdb_test puts an EOL marker right after the pattern, but it doesn't put
any required pattern before the pattern...
Altered the test. Thanks for the tips on irc on doing this.
Patch attached.
Regards
Phil
diff --git a/gdb/c-lang.c b/gdb/c-lang.c
index 8b5410f..d03a88f 100644
--- a/gdb/c-lang.c
+++ b/gdb/c-lang.c
@@ -183,16 +183,20 @@ c_printstr (struct ui_file *stream, const gdb_byte *string,
}
/* 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.
+ buffer in BUFFER, which should be freed by the caller. If length
+ is specified at -1, the string is read until a null character is
+ found, otherwise the string is read to the length specified.
+ If VALUE is an array with a known length, the function will not
+ read past the end of the array. LENGTH will contain the size of
+ the string in bytes. (If a length of -1 is specified, the length
+ returned will not include the null character).
+
+ In the case of length specified as -1, assume 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.
CHARSET is always set to the target charset. */
@@ -204,6 +208,7 @@ c_get_string (struct value *value, gdb_byte **buffer, int *length,
unsigned int fetchlimit;
struct type *type = check_typedef (value_type (value));
struct type *element_type = TYPE_TARGET_TYPE (type);
+ int req_length = *length;
if (element_type == NULL)
goto error;
@@ -249,12 +254,17 @@ c_get_string (struct value *value, gdb_byte **buffer, int *length,
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. */
+ /* If a length is specified, use that. */
+ if (*length >= 0)
+ i = *length;
+ else
+ /* Otherwise, 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 a user-defined length, the number of non-null
+ characters, or FETCHLIMIT. */
*length = i * width;
*buffer = xmalloc (*length);
memcpy (*buffer, contents, *length);
@@ -262,7 +272,7 @@ c_get_string (struct value *value, gdb_byte **buffer, int *length,
}
else
{
- err = read_string (value_as_address (value), -1, width, fetchlimit,
+ err = read_string (value_as_address (value), *length, width, fetchlimit,
buffer, length);
if (err)
{
@@ -272,10 +282,15 @@ c_get_string (struct value *value, gdb_byte **buffer, int *length,
}
}
- /* If the last character is null, subtract it from LENGTH. */
- if (*length > 0
- && extract_unsigned_integer (*buffer + *length - width, width) == 0)
- *length -= width;
+ /* If the LENGTH is specified at -1, we want to return the string
+ length up to the terminating null character. If an actual length
+ was specified, we want to return the length of exactly what was
+ read. */
+ if (req_length == -1)
+ /* If the last character is null, subtract it from LENGTH. */
+ if (*length > 0
+ && extract_unsigned_integer (*buffer + *length - width, width) == 0)
+ *length -= width;
*charset = target_charset ();
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 8509ecc..c7091a6 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -18442,7 +18442,7 @@ The result @code{bar} will be a @code{gdb.Value} object holding the
value pointed to by @code{foo}.
@end defmethod
-@defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]}
+@defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
If this @code{gdb.Value} represents a string, then this method
converts the contents to a Python string. Otherwise, this method will
throw an exception.
@@ -18453,7 +18453,9 @@ language.
For C-like languages, a value is a string if it is a pointer to or an
array of characters or ints. The string is assumed to be terminated
-by a zero of the appropriate width.
+by a zero of the appropriate width. However if the optional length
+argument is given, the string will be converted beyond any embedded
+nulls up to the length specified.
If the optional @var{encoding} argument is given, it must be a string
naming the encoding of the string in the @code{gdb.Value}, such as
@@ -18467,6 +18469,9 @@ will be used, if the current language is able to supply one.
The optional @var{errors} argument is the same as the corresponding
argument to Python's @code{string.decode} method.
+
+If the optional @var{length} argumen is given, the string will be
+fetched and converted to the given length.
@end defmethod
@end table
diff --git a/gdb/language.h b/gdb/language.h
index 85826fd..97b93d6 100644
--- a/gdb/language.h
+++ b/gdb/language.h
@@ -283,10 +283,14 @@ struct language_defn
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). CHARSET will hold the encoding
- used in the string. */
+ buffer in BUFFER, which should be freed by the caller. If LENGTH
+ is specified at -1, the string is read until a null character is
+ found - otherwise the string is read to the length specified.
+ On completion, LENGTH will hold the size in bytes of the string.
+ If a LENGTH of -1 was specified it will count only actual
+ characters, excluding any eventual terminating null character.
+ Otherwise LENGTH will equal all characters - including any nulls.
+ CHARSET will hold the encoding used in the string. */
void (*la_get_string) (struct value *value, gdb_byte **buffer, int *length,
const char **charset);
diff --git a/gdb/python/python-value.c b/gdb/python/python-value.c
index 2eaf15f..743e6a6 100644
--- a/gdb/python/python-value.c
+++ b/gdb/python/python-value.c
@@ -190,13 +190,16 @@ valpy_get_type (PyObject *self, void *closure)
return obj->type;
}
-/* Implementation of gdb.Value.string ([encoding] [, errors]) -> string
- Return Unicode string with value contents. If ENCODING is not given,
- the string is assumed to be encoded in the target's charset. */
+/* Implementation of gdb.Value.string ([encoding] [, errors]
+ [, length]) -> string. Return Unicode string with value contents.
+ If ENCODING is not given, the string is assumed to be encoded in
+ the target's charset. If LENGTH is provided, only fetch string to
+ the length provided. */
+
static PyObject *
valpy_string (PyObject *self, PyObject *args, PyObject *kw)
{
- int length, ret = 0;
+ int length = -1, ret = 0;
gdb_byte *buffer;
struct value *value = ((value_object *) self)->value;
volatile struct gdb_exception except;
@@ -205,10 +208,10 @@ valpy_string (PyObject *self, PyObject *args, PyObject *kw)
const char *errors = NULL;
const char *user_encoding = NULL;
const char *la_encoding = NULL;
- static char *keywords[] = { "encoding", "errors" };
+ static char *keywords[] = { "encoding", "errors", "length" };
- if (!PyArg_ParseTupleAndKeywords (args, kw, "|ss", keywords,
- &user_encoding, &errors))
+ if (!PyArg_ParseTupleAndKeywords (args, kw, "|ssi", keywords,
+ &user_encoding, &errors, &length))
return NULL;
TRY_CATCH (except, RETURN_MASK_ALL)
@@ -975,7 +978,7 @@ static PyMethodDef value_object_methods[] = {
{ "cast", valpy_cast, METH_VARARGS, "Cast the value to the supplied type." },
{ "dereference", valpy_dereference, METH_NOARGS, "Dereferences the value." },
{ "string", (PyCFunction) valpy_string, METH_VARARGS | METH_KEYWORDS,
- "string ([encoding] [, errors]) -> string\n\
+ "string ([encoding] [, errors] [, length]) -> string\n\
Return Unicode string representation of the value." },
{NULL} /* Sentinel */
};
diff --git a/gdb/testsuite/gdb.python/python-value.c b/gdb/testsuite/gdb.python/python-value.c
index 092c520..f3d6284 100644
--- a/gdb/testsuite/gdb.python/python-value.c
+++ b/gdb/testsuite/gdb.python/python-value.c
@@ -44,6 +44,8 @@ main (int argc, char *argv[])
struct s s;
union u u;
PTR x = &s;
+ char st[17] = "divide et impera";
+ char nullst[17] = "divide\0et\0impera";
s.a = 3;
s.b = 5;
diff --git a/gdb/testsuite/gdb.python/python-value.exp b/gdb/testsuite/gdb.python/python-value.exp
index 3421406..59d13c6 100644
--- a/gdb/testsuite/gdb.python/python-value.exp
+++ b/gdb/testsuite/gdb.python/python-value.exp
@@ -234,6 +234,25 @@ proc test_value_in_inferior {} {
# Test address attribute
gdb_test "python print 'result =', arg0.address" "= 0x\[\[:xdigit:\]\]+" "Test address attribute"
+
+ # Test string fetches, both partial and whole.
+ gdb_test "print st" "\"divide et impera\""
+ gdb_py_test_silent_cmd "python st = gdb.history (0)" "get value from history" 1
+ gdb_test "python print st.string ()" "divide et impera" "Test string with no length"
+ gdb_test "python print st.string (length = -1)" "divide et impera" "Test string (length = -1) is all of the string"
+ gdb_test "python print st.string (length = 6)" "divide"
+ gdb_test "python print \"---\"+st.string (length = 0)+\"---\"" "------" "Test string (length = 0) is empty"
+ gdb_test "python print len(st.string (length = 0))" "0" "Test length is 0"
+
+
+ # Fetch a string that has embedded nulls.
+ gdb_test "print nullst" "\"divide\\\\000et\\\\000impera\".*"
+ gdb_py_test_silent_cmd "python nullst = gdb.history (0)" "get value from history" 1
+ gdb_test "python print nullst.string ()" "divide" "Test string to first null"
+ # Python cannot print strings that contain the null (\0) character.
+ # For the purposes of this test, use repr()
+ gdb_py_test_silent_cmd "python nullst = nullst.string (length = 9)" "get string beyond null" 1
+ gdb_test "python print repr(nullst)" "u'divide\\\\x00et'"
}
proc test_value_after_death {} {