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PR 16286

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* c-lang.c (c_get_string): Ignore the declared size of the object
	if a specific length is requested.

	testsuite/
	* gdb.python/py-value.c: #include stdlib.h, string.h.
	(str): New struct.
	(main): New local xstr.
	* gdb.python/py-value.exp (test_value_in_inferior): Add test to
	fetch a value as a string with a length beyond the declared length
	of the array.
This commit is contained in:
Doug Evans 2013-12-10 16:20:08 -08:00
parent 34dc884e17
commit 0987cf3512
5 changed files with 60 additions and 3 deletions
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25
gdb/c-lang.c
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@ -227,9 +227,13 @@ c_printstr (struct ui_file *stream, struct type *type,
until a null character of the appropriate width is found, otherwise
the string is read to the length of characters specified. The size
of a character is determined by the length of the target type of
the pointer or array. If VALUE is an array with a known length,
the function will not read past the end of the array. On
completion, *LENGTH will be set to the size of the string read in
the pointer or array.
If VALUE is an array with a known length, and *LENGTH is -1,
the function will not read past the end of the array. However, any
declared size of the array is ignored if *LENGTH > 0.
On completion, *LENGTH will be set to the size of the string read in
characters. (If a length of -1 is specified, the length returned
will not include the null character). CHARSET is always set to the
target charset. */
@ -309,6 +313,21 @@ c_get_string (struct value *value, gdb_byte **buffer,
{
CORE_ADDR addr = value_as_address (value);
/* Prior to the fix for PR 16196 read_string would ignore fetchlimit
if length > 0. The old "broken" behaviour is the behaviour we want:
The caller may want to fetch 100 bytes from a variable length array
implemented using the common idiom of having an array of length 1 at
the end of a struct. In this case we want to ignore the declared
size of the array. However, it's counterintuitive to implement that
behaviour in read_string: what does fetchlimit otherwise mean if
length > 0. Therefore we implement the behaviour we want here:
If *length > 0, don't specify a fetchlimit. This preserves the
previous behaviour. We could move this check above where we know
whether the array is declared with a fixed size, but we only want
to apply this behaviour when calling read_string. PR 16286. */
if (*length > 0)
fetchlimit = UINT_MAX;
err = read_string (addr, *length, width, fetchlimit,
byte_order, buffer, length);
if (err)