Re: do { quit; } else { }

On 09/04/2025 12:16, Michael S wrote:

On Wed, 9 Apr 2025 11:42:36 +0200
David Brown <david.brown@hesbynett.no> wrote:
 

On 08/04/2025 18:28, bart wrote:

On 08/04/2025 15:50, David Brown wrote:

On 08/04/2025 13:35, bart wrote:
But it is true that some compilers have by default supported an
extension that was designed to make interoperability with Fortran
programs easier

>
Which means a pile of badly written programs.

>
That is why I said it was a bad idea for gcc to have "-fcommon" as
the default.  It is a real shame that it took so long to change it.
>
However, while that default meant that some people wrote C code with
a misunderstanding of linkages and the difference between
declarations and definitions, most C programmers don't make that
mistake.  When gcc eventually changed the default, it did not lead to
wide-spread breakage of code.
>

 I wouldn't be so sure.
I have no statistics, but would expect that very significant part of
Unix-only C programmers, especially grumpy old timers, believes that
'-fcommon' is the real C and the rest are heresies.
 

One of the tests the gcc folk (or other interested parties) do before releasing a new version of gcc is to do a complete rebuild of some Linux distributions - Debian, Red Hat Fedora, and perhaps others.  This can lead to reversal of planned changes to default flags in gcc if there is significant breakage, or to changes in makefiles or build flags for some of the upstream packages if there are only a few packages affected.  So a change of the defaults in gcc is a good indication that very few open source programs are affected by the change - few enough that changing the defaults is worth the effort fixing any conflicting packages.
Of course even Debian does not contain /all/ *nix software, but it certainly covers a lot.
I certainly have seen C code with things like "int x;" in header files, but it is not that common.  After all, plenty of people will tell you how terrible "global variables" are, no matter how they are declared.
A much more common bad style is to have file-scope variables declared as "int x;" inside a C file even though they were not intended to be externally linked - they should have been declared "static int x;". With "-fcommon", if you have coincidentally done that with the same identifier name in more than one translation unit, these will be merged - potentially leading to all kinds of "fun" bugs.  With "-fno-common", you get a link-time error.  This is why "-fno-common" is so important - it makes these code errors visible.
But we have more than a few grumpy old timers in this newsgroup - perhaps some of them would like to chime in if they believe "-fcommon" is how C should be.
(I may be grumpy, and I have grey in my beard and were sandals with socks, but I am not yet an "old timer" by the standards of this group - so my opinion doesn't count!)