I don’t know whether this warning is something which may become an error in future versions, but just in case: mupdf/pdf_cmap_parse.c: In function ‘pdf_parsecodespacerange’: mupdf/pdf_cmap_parse.c:121:11: warning: comparison between ‘pdf_token_e’ and ‘enum <anonymous>’ It complains at each instance of a comparison between a pdf_token_e variable and the anonymous enum declared at the top of pdf_cmap_parse.c.