> char *passwd;
> MD5Update(&md5ctx, passwd, strlen(passwd));

> and according to the manpage: 
> MD5Update(MD5_CTX *context, const unsigned char *data, unsigned int len);

> So what is the right fix for this?

In this particular case, I would say the right fix is to make MD5Update
take a const void *.

More generally, I would say your assumption

> My assumption is that each instance of this should be fixed in the
> source.

is right.

> Or is there a compiler option I should use instead to skip past these
> warnings?

Check the docs; lots of warnings have -Wno-* forms.

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