The question is in the title. For example, as explained here gcc unrecognized command line options '-V' and '-qversion' with autoconf, the error message gcc: error: unrecognized command line option '-V' is, if I understood correctly, an artifact of autoconf trying to figure out the compiler version, not a real error. Is there a list or some reliable trick to figure out those error messages that can be ignored? The answer to a related question here Slackware ./configure error is not very informative, even missing the point. Better, is there a way, without having to change the entire setting, to eliminate these uninformative error messages. It is not my setting. In this case, it is the setting of the excellent Videolan VLC project.
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Dominic108
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based on your link, this is expected behavior, and most people ignore it. it does look like the second answer does provide a script for better behavior, if you have the right version and know where to drop the script in. https://superuser.com/a/1209619/171793 . You could alter this script to check for only the option available to your version of gcc if you wanted to. – Frank Thomas Mar 25 '21 at 20:37
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Note though, there is nothing about these failures that indicates that they are "optional". they are real errors, so there isn't some config setting you could set to shut them up. the script in question handles the error stream, so if you are trying to avoid editing that script, you are probably not going to get the outcomes you want. – Frank Thomas Mar 25 '21 at 21:04
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They are not real errors. They are fake errors. They are tests. For example, the -V option does not exist in gcc since April 2013 and it was used only to see if an old version of gcc is used. The actual configuration does not use this option at all. It is used in a fake call to gcc. Well, it is a real call, but only for testing. – Dominic108 Mar 25 '21 at 21:33
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Oh well, here is what I discovered. All the tests done in the configure file that is generated by autoconf have their output redirected to some other streams than stdout or stderr. This means that they are not in the output that is sent to the terminal. So, to have a file without the output of these tests one can redirect the output streams stderr and stdout of configure to the file, for example: ./configure > config_.log 2>&1. You will still see the conclusion of these tests, because these are sent to stdin or stderr. In particular, in this manner, I don't see the fake error gcc: error: unrecognized command line option '-V' anymore, but I see the result of the test.
Dominic108
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