Re: [ANN] Lua 5.3.0 (rc2) now available
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: [ANN] Lua 5.3.0 (rc2) now available
- From: Jean-Luc Jumpertz <jean-luc@...>
- Date: Thu, 1 Jan 2015 14:12:39 +0100
> Le 31 déc. 2014 à 19:19, Roberto Ierusalimschy <roberto@inf.puc-rio.br> a écrit :
>
>>> There is one warning on Mac OS X (10.10) when compiling in Xcode 6.1.1 with default warnings enabled:
>>>
>>> /Users/jean-luc/Developpement/lua-5.3.0 - xcode/src/liolib.c:480:16: warning: variable 'c' may be uninitialized when used here [-Wconditional-uninitialized]
>>> if (!chop && c == '\n') /* want a newline and have one? */
>>> ^
>>> /Users/jean-luc/Developpement/lua-5.3.0 - xcode/src/liolib.c:467:8: note: initialize the variable 'c' to silence this warning
>>> int c;
>>> ^
>>> This is a false positive, but hard for the compiler to detect that c is always initialized… :-)
>>
>> It is not that hard: the only branch in the path from the function head
>> to the first assignment to 'c' is obviously false (jump if not (0 <
>> some-non-zero-constant)). I am afraid that solving this warning with
>> a useless initialization can generate warnings in smarter compilers
>> ("value is never used"). I tried to change the code to make it more
>> "obvious" that 'c' cannot be used uninitialized, but could not find a
>> good solution.
>
Agreed: the issue is clearly on the compiler’s side.
Therefore I filled a bug about this incorrect warning in Xcode/Clang.
> You can try this, but in my view it is hardly an improvement...
>
> --- liolib.c 2014年11月21日 12:17:33 2.141
> +++ liolib.c 2014年12月31日 18:17:02
> @@ -470,8 +470,11 @@
> char *buff = luaL_prepbuffer(&b); /* pre-allocate buffer */
> int i = 0;
> l_lockfile(f); /* no memory errors can happen inside the lock */
> - while (i < LUAL_BUFFERSIZE && (c = l_getc(f)) != EOF && c != '\n')
> + do {
> + if ((c = l_getc(f)) == EOF || c == '\n')
> + break;
> buff[i++] = c;
> + } while (i < LUAL_BUFFERSIZE);
> l_unlockfile(f);
> luaL_addsize(&b, i);
> if (i < LUAL_BUFFERSIZE)
>
>
> -- Roberto
I prefer the current version too.
Jean-Luc