On 18 December 2024 at 19:46, Bielow, Chris wrote:
| hoping this is the right place for this:
| I stumbled upon documentation regarding the use of `assert` in C++ code, in
| particular, https://cran.r-project.org/web/packages/policies.html states
| that
|
| ```
| Thus C/C++ calls to assert/abort/exit/std::terminate, Fortran calls to STOP
| and so on must be avoided.
| ```
|
| , which goes against all best practice guidelines I'm aware of.
Yes and no.
Defensize programming is good, of course, but `assert()` leads to an
`abort()` and immediate abort which for an _environment_ such as R is really
not appropriate. You want a proper error return (i.e. Rf_error with a message
or alike) to the R prompt.
Note that you can always test something like this; there are several packages
allowing ad-hoc compilation from `inline` to `Rcpp` and others. So here:
> Rcpp::cppFunction(r"(void ohnoes() { assert(false); })", includes=c("#undef
NDEBUG", "#include <assert.h>"))
> ohnoes()
R: file2cd1353560062b.cpp:8: void ohnoes(): Assertion `false' failed.
Process R:3 aborted (core dumped) at Wed Dec 18 16:22:19 2024
... and that took my R session down just like `assert()` is expected. Also
note the trickery I had to do to re-enable `assert()` by undefining `NDEBUG`
and including the header after that.
So viewed from that angle, it really is not against _best practices for R
extensions_ which is what the CRAN Policy is about.
Cheers, Dirk
| Therefore I would propose to remove 'assert' from the above statement.
| In support, https://cran.r-project.org/doc/manuals/r-release/R-exts.html
| states that
|
| ```
| One usage that could call abort is the assert macro in C or C++ functions,
| which should never be active in production code. The normal way to ensure
| that is to define the macro NDEBUG, and R CMD INSTALL does so as part of the
| compilation flags.
| ```
| which seems a reasonable thing to do.
|
| As a sidenote, the guide could be extended to encourage new mechanisms
| available in modern C++ like `static_assert`.
|
|
| Cheers
| Chris
|
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--
dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
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