Comments on: The peril of index(3) http://boredzo.org/blog/archives/2009-11-05/the-peril-of-the-index-function The personal weblog of Peter Hosey. Wed, 09 May 2012 18:26:35 +0000 hourly 1 http://wordpress.org/?v=3.1 By: Jonathan Mitchell http://boredzo.org/blog/archives/2009-11-05/the-peril-of-the-index-function/comment-page-1#comment-296839 Jonathan Mitchell Tue, 08 Dec 2009 23:14:15 +0000 http://boredzo.org/blog/?p=1135#comment-296839 GCC 4.2 as shipped with Xcode 3.2.1 does shadow your local variables as well as parameters and globals. Warn whenever a local variable shadows another local variable, parameter or global variable or whenever a built-in function is shadowed. [GCC_WARN_SHADOW, -Wshadow] GCC 4.2 as shipped with Xcode 3.2.1 does shadow your local variables as well as parameters and globals.

Warn whenever a local variable shadows another local variable, parameter or global variable or whenever a built-in function is shadowed. [GCC_WARN_SHADOW, -Wshadow]

]]> By: Jens Alfke http://boredzo.org/blog/archives/2009-11-05/the-peril-of-the-index-function/comment-page-1#comment-294880 Jens Alfke Fri, 13 Nov 2009 23:17:32 +0000 http://boredzo.org/blog/?p=1135#comment-294880 I disagree. If you can pass a pointer as an array index and not get a compile error, something's dangerously wrong with your build process. This is why I ALWAYS, ALWAYS build with -Werror ("Treat warnings as errors".) There are too many things GCC treats as warnings that are very dangerous and should be fixed immediately. This goes double for Obj-C programming, where things like misspelled selectors only generate warnings. I find the shadowing warning useless because it yells about all sorts of names that happen to be used by C and POSIX APIs — not just index but time and a bunch of others. I'd like to have a warning that told me when I was shadowing my own local variables, but I don't think GCC has that. I disagree. If you can pass a pointer as an array index and not get a compile error, something’s dangerously wrong with your build process. This is why I ALWAYS, ALWAYS build with -Werror (“Treat warnings as errors”.) There are too many things GCC treats as warnings that are very dangerous and should be fixed immediately. This goes double for Obj-C programming, where things like misspelled selectors only generate warnings.

I find the shadowing warning useless because it yells about all sorts of names that happen to be used by C and POSIX APIs — not just index but time and a bunch of others. I’d like to have a warning that told me when I was shadowing my own local variables, but I don’t think GCC has that.

]]> By: Peter Hosey http://boredzo.org/blog/archives/2009-11-05/the-peril-of-the-index-function/comment-page-1#comment-294278 Peter Hosey Fri, 06 Nov 2009 04:52:31 +0000 http://boredzo.org/blog/?p=1135#comment-294278 I haven't had the compiler throw an error about it once, except when I build with “Treat Warnings as Errors” turned on (which is good for many reasons, including this one). But I have encountered the crash. Less time spent fixing oops-my-variable-declaration-went-missing bugs is more time spent fixing real bugs and adding features. And <code>idx</code> really isn't <em>that</em> unreadable, although I do try to consider whether <code>fooIndex</code> or <code>indexOfFoo</code> might be better without being obnoxiously long. The main thing is to not use <code>index<code>. I haven’t had the compiler throw an error about it once, except when I build with “Treat Warnings as Errors” turned on (which is good for many reasons, including this one). But I have encountered the crash. Less time spent fixing oops-my-variable-declaration-went-missing bugs is more time spent fixing real bugs and adding features.

And idx really isn’t that unreadable, although I do try to consider whether fooIndex or indexOfFoo might be better without being obnoxiously long. The main thing is to not use index.

]]> By: Andy Finnell http://boredzo.org/blog/archives/2009-11-05/the-peril-of-the-index-function/comment-page-1#comment-294277 Andy Finnell Fri, 06 Nov 2009 04:48:20 +0000 http://boredzo.org/blog/?p=1135#comment-294277 I see what your saying, but if you remove your declaration of index (accidental or otherwise) you get all sorts of warnings about trying to use a pointer as an integer (at least I did when I tried it). Depending on what you try to do with index (such as math) the compiler will even throw errors. I can appreciate that you've been bitten by this before, but this seems really edge case. I prefer to have readable names, and trust the compiler will catch my mistakes. I see what your saying, but if you remove your declaration of index (accidental or otherwise) you get all sorts of warnings about trying to use a pointer as an integer (at least I did when I tried it). Depending on what you try to do with index (such as math) the compiler will even throw errors. I can appreciate that you’ve been bitten by this before, but this seems really edge case. I prefer to have readable names, and trust the compiler will catch my mistakes.

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