Use after free error

[Xazax-hun]

I am working on some new compiler warnings and stumbled upon the following warning:

P0267_RefImpl/P0267_RefImpl/P0267_RefImpl/cairo/xlib/xio2d_cairo_xlib_output_surfaces.h

Line 329 in add3c97

auto es = clientMsgStr.str().c_str();

/home/tgahor/data/projects/P0267_RefImpl/P0267_RefImpl/P0267_RefImpl/cairo/xlib/xio2d_cairo_xlib_output_surfaces.h:329:19: warning: object backing the pointer will be destroyed at the end of the full-expression [-Wdangling]
                                                                auto es = clientMsgStr.str().c_str();
                                                                          ^~~~~~~~~~~~~~~~~~

This looks like a true positive as the pointer returned by c_str() will dangle after the end of the full expression.