documentclass[10pt,a5paper,twoside]{memoir}

usepackage[T1]{fontenc}
usepackage[utf8]{inputenc}

usepackage[brazil]{babel}
usepackage[showframe,pass]{geometry}

newififdebug
debugtrue
% debugfalse

ifdebug
    % defincludegraphics{includegraphics}
    newcommand{includegraphics}{includegraphics}
elsefi

begin{document}

    includegraphics[width=linewidth]{pictures/ex01}

end{document}

! Missing number, treated as zero.
<to be read again>
                   ]
l.86     includegraphics[width=linewidth]
                                           {pictures/ex01}
A number should have been here; I inserted `0'.
(If you can't figure out why I needed to see a number,
look up `weird error' in the index to The TeXbook.)

! Illegal unit of measure (pt inserted).
<to be read again>
                   ]
l.86     includegraphics[width=linewidth]
                                           {pictures/ex01}
Dimensions can be in units of em, ex, in, pt, pc,
cm, mm, dd, cc, nd, nc, bp, or sp; but yours is a new one!
I'll assume that you meant to say pt, for printer's points.
To recover gracefully from this error, it's best to
delete the erroneous units; e.g., type `2' to delete
two letters. (See Chapter 27 of The TeXbook.)

@ifundefined{longtable}
{
    newenvironment{longtable}[0]
        {longtable environmentparverbatimtiny}
        {endverbatimendgrafnormalfont replacement for debug mode}
}{}