On 20/12/2017 17:42, Winston Chang wrote:
On recent builds of R-devel, R CMD check gives a WARNING when some
compiler warning flags are detected, such as -Werror, because they are
non-portable. This appears to have been added in this commit:
https://github.com/wch/r-source/commit/2e80059
That is not the canonical R sources. And your description seems wrong:
there is now an _optional_ check controlled by an environment variable,
primarily for CRAN checks.
I'm working on a package where these compiler warning flags are
present in a Makefile generated by a configure script -- that is, the
configure script detects whether the compiler supports these flags,
and if so, puts them in the Makefile. (The configure script is for a
third-party C library which is in a subdirectory of src/.)
Because the flags are added only if the system supports them, there
shouldn't be any worries about portability in practice.
Please read the explanation in the manual: there are serious concerns
about such flags which have bitten CRAN users several times.
To take your example, you cannot know what -Werror does on all compilers
(past, present or future) where it is supported (and -W flags do do
different things on different compilers). On current gcc it does
-Werror
Make all warnings into errors.
and so its effect depends on what other flags are used (people typically
use -Wall, and most new versions of both gcc and clang add more warnings
to -Wall -- I read this week exactly such a discussion about the
interaction of -Werror with -Wtautological-constant-compare as part of
-Wall in clang trunk).
Is there a way to get R CMD check to not raise warnings in cases like
this? I know I could modify the C library's configure.ac (which is
used to generate the configure script) but I'd prefer to leave the
library's code untouched if possible.
You don't need to (and most likely should not) use the C[XX]FLAGS it
generates ... just use the flags which R passes to the package to use.
-Winston
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Emeritus Professor of Applied Statistics, University of Oxford
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