In `read_next_b64_code()`, the result of fgetc() is stored into a char,
but later compared against EOF, which is generally -1. On platforms
where char is unsigned, this generates a compiler warning/error that the
comparison will never be true (causing a build failure). The value will
never match, with the function ultimately bailing with a "Too many bad
symbols are detected" error.
On platforms with signed char, EOF is detected, but a file containing a
0xFF character will causes a premature end of file exit of the loop.
Fix this by changing the result to an int.
Fixes#3794.
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: David Brown <david.brown@linaro.org>
