[gparted] Workaround g_utf8_find_next_char() not incrementing past NUL char (#777973)

[Curtis Gedak <gedakc src gnome org>]

commit 3a6a304c64b669f71c530a07d64caa93dc2f23ca
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Mon Mar 13 22:24:23 2017 +0000

    Workaround g_utf8_find_next_char() not incrementing past NUL char (#777973)
    
    If PipeCapture reads a NUL character, a valid UTF-8 character, it causes
    GParted to allocate all available memory and crash.  The while loop in
    PipeCapture::OnReadable() loops forever reading the same NUL character
    from readbuf because g_utf8_find_next_char() doesn't advance past it.
    Hence an infinite number of NUL characters are added to the current
    line, linevec.
    
    Workaround this by checking for this failure case of
    g_utf8_find_next_char() and increment past the NUL character.
    
    This is actually a bug recently fixed in glib 2.49.3 released
    2016-07-17.  References:
    
    *   Bug 547200 - g_utf8_find_next_char() issues
        https://bugzilla.gnome.org/show_bug.cgi?id=547200
    
    *   https://git.gnome.org/browse/glib/commit/?id=e0e652e4032a181d4f0b0a12aeddf0678b7a3c04
        Fix a corner-case in g_utf8_find_next_char
    
        In the case that *p is '\0', we should return p + 1, not p.
        This change allows to simplify g_utf8_find_next_char a bit.
    
    Bug 777973 - Segmentation fault on bad disk

 src/PipeCapture.cc |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/src/PipeCapture.cc b/src/PipeCapture.cc
index 69cf741..b900a7d 100644
--- a/src/PipeCapture.cc
+++ b/src/PipeCapture.cc
@@ -144,7 +144,13 @@ bool PipeCapture::OnReadable( Glib::IOCondition condition )
                        else
                        {
                                // Advance read pointer past the read UTF-8 character.
-                               read_ptr = g_utf8_find_next_char( read_ptr, end_ptr );
+                               const char * new_ptr = g_utf8_find_next_char( read_ptr, end_ptr );
+                               if ( new_ptr == read_ptr && *read_ptr == '\0' )
+                                       // Workaround bug in g_utf8_find_next_char() which
+                                       // stops it advancing past NUL char in buffer
+                                       // delimited by an end pointer.
+                                       new_ptr ++;
+                               read_ptr = new_ptr;
                                if ( read_ptr == NULL )
                                        read_ptr = end_ptr;
                        }