Error messaging suggestion

[jrowen]

This is a nice-to-have suggestion for those of us having less C++ experience and currently using older environments (like RHEL6). When there is a problem compiling a package, could the error messaging be enhanced to check the compiler version and let the user know when he/she may be using an older, unsupported version of the compiler? This info could save a lot of debugging/Google time.

This suggestion was inspired by this issue.

[eddelbuettel]

Two answers:

• Yes, and pull requests welcome. We already test different compilers and you could hook into the next block there and at least warn if versions older than 4.6.2 (== oldest known CRAN compiler) are used.
• No, as Rcpp is eclectic. We don't always use all features, and different projects have different requirements. With that I think an error would be wrong, but maybe a warning for truly old compilers?

To be discussed, cc'ing @jjallaire and @kevinushey

[kevinushey]

I'd be happy with warning on gcc <= 4.6.2.

[coatless]

On this, it seems like a quick fix would be:

#pragma message "WARNING: GCC Compiler Version <= 4.6.2"

As:

#warning "GCC Compiler Version <= 4.6.2"

might not be supporte.

In addition, the #error directive would kill the compilation. (Tagging #506)

[eddelbuettel]

In the meantime, "systematically most important" dependent package RcppArmadillo added its own checks to fail those with g++ 4.4 and alike.

That said, I really do like what @mattdowle and @arunsrinivasan are doing with data.table and their arch-conservative dependencies ... supporting everything down to R 2.15 which I think was used during Napoleon's reign. Of course they have it easier with C than we do but still -- avoiding semi-arbitrary boundaries is a good thing.

In essence, old RHEL systems are at the same time really stupid and still fairly common. The longer we can accommodate with minimal pain, the better. (RcppArmadillo has no choice as Armadillo drew a line).

[coatless]

@eddelbuettel :

Per /inst/include/armadillo_bits/compiler_setup.hpp.

  #if (ARMA_GCC_VERSION < 40600)
    #pragma message ("WARNING: this compiler is OUTDATED and has INCOMPLETE support for the C++ standard;")
    #pragma message ("WARNING: if something breaks, you get to keep all the pieces.")
  #endif

The proposed #pragma message will be aokay?

[eddelbuettel]

Yes 🍰

[coatless]

Per discussion in PR #515, due to the way RHEL is structured coupled with the fact that Rcpp's code base working with GCC 4.6.2, this will not be fixed. In the event that this changes, the code in PR #515 can be used in the future.

Please close. (Tagging #506)