If you don't use all the dialogf() formats, then you can declare a list of all formats that you use so that the others don't get linked into the executable. This will only save up to about 10 KB, but see Allegro's documentation (the "Reducing your executable size" section) for more hints on how to get rid of much more size. The list of formats should look like this:
BEGIN_DIALOGF_FORMAT_LIST
format1
format2
etc...
END_DIALOGF_FORMAT_LIST
where format1, format2 etc are any of the macros:
DIALOGF_FORMAT_BOOL DIALOGF_FORMAT_STRING DIALOGF_FORMAT_FILENAME DIALOGF_FORMAT_VLIST DIALOGF_FORMAT_LIST DIALOGF_FORMAT_DATAFILE DIALOGF_FORMAT_WVLIST DIALOGF_FORMAT_WLIST DIALOGF_FORMAT_WDATAFILE DIALOGF_FORMAT_DIALOGF DIALOGF_FORMAT_VDIALOGF DIALOGF_FORMAT_INT DIALOGF_FORMAT_PINT DIALOGF_FORMAT_UINT DIALOGF_FORMAT_PUINT DIALOGF_FORMAT_SHORT DIALOGF_FORMAT_PSHORT DIALOGF_FORMAT_USHORT DIALOGF_FORMAT_PUSHORT DIALOGF_FORMAT_CHAR DIALOGF_FORMAT_PCHAR DIALOGF_FORMAT_UCHAR DIALOGF_FORMAT_PUCHAR DIALOGF_FORMAT_DOUBLE DIALOGF_FORMAT_PDOUBLE DIALOGF_FORMAT_FLOAT DIALOGF_FORMAT_PFLOAT DIALOGF_FORMAT_LINE DIALOGF_FORMAT_NOTHINGLike in Allegro, this will only work for the statically linked library.