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This is a really good point actually, aren't there static analysis tools that can figure out things like this? I know in JS we have linters to stop you from doi

This is a really good point actually, aren't there static analysis tools that can figure out things like this? I know in JS we have linters to stop you from doing things that are most likely not very smart. I find this very useful, a lot more useful than to say "If you don't even read the manpages there is no help in sight". Maybe the compiler should not do it but perhaps you could run a linter against packages that are shipped with an os to find issues like this easier.

jstimpfle 9y ago
It's pretty likely that there are tools which can (attempt to) detect this. The question is why aren't these tools used. The answer is because they are expensive, and using them implies development costs as well - learning the tool, setting it up to filter out false positives, setting it up to run in an automated way, structuring the code differently so that the tool is happy (which can lead to worse structure), making sure all the remaining false positives aren't problems every time the tool is run. It's not what you do in an open source project that has a few lines of C code.
maxlybbert 9y ago
C has separate compilation: the compiler isn’t guaranteed to have all of the relevant source code at one time. When the signal handler is compiled, there’s nothing to say “this will be used as a signal handler,” so while the compiler has the source it doesn’t have a reason to complain about calling any particular functions. Then, when that function is used as a signal handler, the compiler has the source to the calling code (well, the code setting up the callback) but may not have the source for the handler itself. So now it knows which rules apply but may not have the code it needs to enforce those rules. If they’re in the same file, it could. And while that is a common case, it’s not the only possibility. How much should the compiler or linter know about the platform’s API? How can I tell the compiler about any arbitrary rule my own code must follow? As someone else suggested, you could do it with annotations, but that’s nonstandard.
tejasmanohar 9y ago
I don't think there's a purely technical reason a non-standard linter cannot exist, but it's probably a large investment to build such a tool (filtering false positives, etc.) and no one has made one sufficiently good and popular enough to be used for a simple one-file-utility.

jstimpfle 9y ago

It's pretty likely that there are tools which can (attempt to) detect this. The question is why aren't these tools used. The answer is because they are expensive, and using them implies development costs as well - learning the tool, setting it up to filter out false positives, setting it up to run in an automated way, structuring the code differently so that the tool is happy (which can lead to worse structure), making sure all the remaining false positives aren't problems every time the tool is run. It's not what you do in an open source project that has a few lines of C code.

maxlybbert 9y ago

C has separate compilation: the compiler isn’t guaranteed to have all of the relevant source code at one time. When the signal handler is compiled, there’s nothing to say “this will be used as a signal handler,” so while the compiler has the source it doesn’t have a reason to complain about calling any particular functions. Then, when that function is used as a signal handler, the compiler has the source to the calling code (well, the code setting up the callback) but may not have the source for the handler itself. So now it knows which rules apply but may not have the code it needs to enforce those rules. If they’re in the same file, it could. And while that is a common case, it’s not the only possibility. How much should the compiler or linter know about the platform’s API? How can I tell the compiler about any arbitrary rule my own code must follow? As someone else suggested, you could do it with annotations, but that’s nonstandard.

tejasmanohar 9y ago

I don't think there's a purely technical reason a non-standard linter cannot exist, but it's probably a large investment to build such a tool (filtering false positives, etc.) and no one has made one sufficiently good and popular enough to be used for a simple one-file-utility.