A handful of small changes to make it compile clearly with the
following parameters:

CFLAGS="-O0 -g -ggdb -fno-common -Wall -Wdeclaration-after-statement
-Wextra -Wformat=2 -Winit-self -Winline -Wpacked
-Wp,-D_FORTIFY_SOURCE=2 -Wpointer-arith -Wlarger-than-65500
-Wmissing-declarations -Wmissing-format-attribute -Wmissing-noreturn
-Wmissing-prototypes -Wnested-externs -Wold-style-definition
-Wredundant-decls -Wsign-compare -Wstrict-aliasing=2
-Wstrict-prototypes -Wundef -Wwrite-strings"