The debugging code:

  vte_debug_print (...)

expands to:

  if (condition)
    ...

This means that code that depends on VTE_DEBUG being defined will still get compiled. For instance, the newly added to_string() methods exist only if VTE_DEBUG is defined, but debugging printouts still call them.

This breaks the compilation of VTE on GNOME Continuous:

../../src/vte.cc: In member function 'void VteTerminalPrivate::invalidate_match_span()':
../../src/vte.cc:5764:71: error: 'struct vte::grid::span' has no member named 'to_string'
                          "Invalidating match span %s\n", m_match_span.to_string());
                                                                       ^
../../src/debug.h:87:56: note: in definition of macro '_vte_debug_print'
  G_STMT_START { _VTE_DEBUG_IF(flags) g_printerr(fmt, ##__VA_ARGS__); } G_STMT_END
                                                        ^
../../src/vte.cc: In member function 'void VteTerminalPrivate::match_hilite_update(long int, long int)':
../../src/vte.cc:5852:35: error: 'struct vte::grid::span' has no member named 'to_string'
     "Matched %s.\n", m_match_span.to_string());
                                   ^
../../src/debug.h:87:56: note: in definition of macro '_vte_debug_print'
  G_STMT_START { _VTE_DEBUG_IF(flags) g_printerr(fmt, ##__VA_ARGS__); } G_STMT_END
                                                        ^
../../src/vte.cc:5857:67: error: 'struct vte::grid::span' has no member named 'to_string'
                                  "No matches %s.\n", m_match_span.to_string());
                                                                   ^
../../src/debug.h:87:56: note: in definition of macro '_vte_debug_print'
  G_STMT_START { _VTE_DEBUG_IF(flags) g_printerr(fmt, ##__VA_ARGS__); } G_STMT_END