On 10/10/22 05:55, Volker Hilsheimer via Development wrote:
Hi,
We are using `#pragma once` in a number of examples and tests in the Qt source
tree, but I don’t think we have officially endorsed it in favour of explicit
include guards.
#pragma once is “non-standard but widely supported” [1], with some caveats,
e.g. when there are multiple header files with the same name (which each
compiler then handles differently, as there is no standard).
From what I see, it should in practice be ok to use. But perhaps I’m missing
something. Does anything speak against using ‘#pragma once’ in new files?
Speaking as co-maintainer of CMake, we have effectively required #pragma
once to build CMake itself since August 2017, we officially codified
this as policy in September 2020, and we will soon be writing a
clang-tidy plugin to enforce this in our CI. We have not received any
complaints about it. Just my $0.02.
Kyle
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