Suppress compiler warning when compiling common/url.c - url_decode with MSVC

[vjardin]

I am not fully familiar yet with all the design of p11-kit, but this code looks strange:

p11-kit/common/url.c

Line 85 in 17b2edb

*p = (a - HEX_CHARS_UPPER) << 4;

It is highlighted by Microsoft cl.exe compiler:

p11-kit\common\url.c(85): warning C4244: '=' : conversion de '__int64' en 'unsigned char', perte possible de données

(which means conversiion from __int64 to unsigned char, possible lost of information

the compiler is right because:
const static char HEX_CHARS_UPPER[] = "0123456789ABCDEF";

Please, what's the idea or purpose of this code ? I see there are some unit tests, but it does not cover this case.

[ueno]

It is the most common path and covered actually: https://coveralls.io/builds/25648864/source?filename=common/url.c

The code is parsing a single byte encoded in hex. Suppose it is %AB. First it looks up the occurrence of A in HEX_CHARS_UPPER and assigns it to a. a - HEX_CHARS_UPPER then means a value of the left nibble (0xA). Do the same for 'B' and finally combine them as a single byte ((0xA << 4) | 0xB).

I think it is a false-positive of the compiler.

[vjardin]

You are right. I get the point. I think I have an idea to avoid this compiler warning. I'll provide a patch soon.

[vjardin]

I'll send a fix after the pull request #251

[winner658]

这个issue完成修复了么，修复在哪里了