Messages in this thread | | | Date | Mon, 24 Feb 2003 16:33:35 -0500 (EST) | From | "Richard B. Johnson" <> | Subject | Re: [PATCH] s390 (7/13): gcc 3.3 adaptions. |
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On Mon, 24 Feb 2003, Linus Torvalds wrote:
> > On Mon, 24 Feb 2003, Richard B. Johnson wrote: > > > > I think you must keep these warnings in! There are many bugs > > that these uncover uncluding loops that don't terminate correctly > > but seem to work for "most all" cases. These are the hard-to-find > > bugs that hit you six months after release. > > At least historically gcc has been so f*cking bad at the "unsigned vs > signed" warnings that they are totally useless. > > Maybe things are better in gcc-3.3. > > Maybe not. > > > > size_t i; > > > > while((i = do_forever()) > 0) > > ; > > > > ... do_forever() finally errors out and returns -1 stuck(forever). > > Does gcc still warn about things like > > #define COUNT (sizeof(array)/sizeof(element)) > > int i; > for (i = 0; i < COUNT; i++) > ... > > where COUNT is obviously unsigned (because sizeof is size_t and thus > unsigned)? > > Gcc used to complain about things like that, which is a FUCKING DISASTER. > > Any compiler that complains about the above should be shot in the head, > and the warning should be killed. > > Linus >
Well yes. And it's correct. Variable `i' in the following code should be a 'size_t'.
Script started on Mon Feb 24 16:23:19 2003 # cat xxx.c #define ArraySize(a) (sizeof(a) / sizeof(a[0])) int foo[12] = {0,}; int count() { int i; for(i=0; i< ArraySize(foo); i++) ; return i; }
# gcc -Wall -Wsign-compare -c -o xxx.o xxx.c xxx.c: In function `count': xxx.c:11: warning: comparison between signed and unsigned # exit exit Script done on Mon Feb 24 16:23:50 2003
... and we all know that it's dumb to do: for(i=0; i< (int) ArraySize(foo); i++) ... just to placate a compiler. But the compiler did find what could-have-been a real problem so the compiler is, indeed, correct.
Maybe what is needed is -Wsign-compare and -Wsign-strict, where -Wsign-compare warns of obvious errors that could cause continuous loops, etc., and -Wsign-strict acts like the current -Wsign-compare. I agree that the current -Wsign-compare is way too strict for the usual coding style where most int compares are "don't care" things that are not worth casts.
Cheers, Dick Johnson Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips). Why is the government concerned about the lunatic fringe? Think about it.
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