As it happened, I had a prepared a similar patch. Attached. Perhaps we could compare patches.
J'
On Sat, May 05, 2012 at 10:14:57PM -0700, Ben Pfaff wrote:
John Darrington <j...@darrington.wattle.id.au> writes:
> Looking at the bug recently reported on bug-gnu-pspp I notice the
following.
>
> Valgrind reports:
I sent out a 2-patch series that fixes the problem that I see,
with and without valgrind. Does it fix the problem you see too?
Thanks,
Ben.
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diff --git a/src/language/lexer/lexer.c b/src/language/lexer/lexer.c
index e72a3e4..7048d8a 100644
--- a/src/language/lexer/lexer.c
+++ b/src/language/lexer/lexer.c
@@ -1217,6 +1217,9 @@ lex_source_read__ (struct lex_source *src)
n = src->reader->class->read (src->reader, &src->buffer[head_ofs],
src->allocated - head_ofs,
segmenter_get_prompt (&src->segmenter));
+
+ assert (n <= src->allocated - head_ofs);
+
if (n == 0)
{
/* End of input.
diff --git a/src/ui/gui/psppire-lex-reader.c b/src/ui/gui/psppire-lex-reader.c
index ae043b0..6351094 100644
--- a/src/ui/gui/psppire-lex-reader.c
+++ b/src/ui/gui/psppire-lex-reader.c
@@ -66,26 +66,47 @@ lex_gtk_text_buffer_read (struct lex_reader *r_, char *buf, size_t n,
enum prompt_style prompt_style UNUSED)
{
struct lex_gtk_text_buffer_reader *r = lex_gtk_text_buffer_reader_cast (r_);
- int n_chars = n;
char *s;
GtkTextIter iter = r->start ;
- int offset = gtk_text_iter_get_offset (&iter);
- int end_offset = gtk_text_iter_get_offset (&r->stop);
-
- if ( end_offset - offset < n)
- n_chars = end_offset - offset;
-
- gtk_text_iter_set_offset (&iter, offset + n_chars);
-
- s = gtk_text_iter_get_text (&r->start, &iter);
-
- strncpy (buf, s, n_chars);
+ const gint offset = gtk_text_iter_get_offset (&iter);
+ const gint end_offset = gtk_text_iter_get_offset (&r->stop);
+ const gint n_bytes = (end_offset - offset < n) ? end_offset - offset : n;
+
+ /* We want to get no more than n_bytes from the buffer.
+ However, since gtk_text_iter deals in chars, not bytes, we cannot possibly
+ set an iter which we know will not fetch too many bytes. Thus, we start
+ by assuming that n_chars == n_bytes and step backwards if we end up fetching
+ too many.
+ */
+ gint n_chars = n_bytes;
+ gint backstep = 4;
+ gint bytes_read = 0;
+ do
+ {
+ gtk_text_iter_set_offset (&iter, offset + n_chars);
+
+ s = gtk_text_iter_get_text (&r->start, &iter);
+ bytes_read = strlen (s);
+ if ( n_chars == 1 && bytes_read > n_bytes)
+ {
+ g_critical ("Reading a single character returned %d bytes, but only %d bytes"
+ " were requested", bytes_read, n_bytes);
+ return 0;
+ }
+ n_chars -= backstep;
+ if ( n_chars < 1)
+ n_chars = 1;
+ backstep *= 2;
+ }
+ while (bytes_read > n_bytes);
+
+ strncpy (buf, s, bytes_read);
r->start = iter;
- return strlen (s);
+ return bytes_read;
}
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