undefined behavior in builtin/am.c

[Roland Illig <roland.illig@gmx.de>]

Hi,

builtin/am.c says:
 > static int str_isspace(const char *str)
 > {
 > 	for (; *str; str++)
 > 		if (!isspace(*str))
 > 			return 0;
 >
 > 	return 1;
 > }

The macro 'isspace' must only be called with an integer representable as
an 'unsigned char', or with the value of the macro EOF.

On platforms where plain 'char' is a signed integer type, any character
whose value is negative invokes undefined behavior (except for the one
character that by coincidence has the same value as the macro EOF).

To fix this, write '!isspace((unsigned char)*str)' instead.

I have no idea how to trigger this part of the code but for someone who
knows this part of Git, it should be easy. Depending on the platform,
this kind of error may be silently ignored or crash the program, as
always with undefined behavior.

Roland