On Sat, 26 Sep 2009, Murray Efford wrote:
A package I have written makes considerable use of external C code. There appear to be no problems building a Windows binary with the GNU C compiler, but now I would like to make the package available for other platforms. A stringent check of the code with the gcc options '-Wall -pedantic' flags many nested functions and variable-length arrays that are not allowed in ISO C. Is it essential that distributed C source code for R packages conforms to ISO C in this respect? I'm working in Windows XP with R2.9.2 and Rtools 2.9.
Yes, it is essential. R does not assume gcc, and it does not even assume gcc 4.x (and people are still using gcc 3.x on some platforms, e.g. the sunfreeware R builds). This is why we publish test result on CRAN for a completely different compiler (from SunPro).
However, if is not clear which standard you mean by 'ISO C': assuming C99 is fairly safe, but GNU extensions from C99 are not -- nested functions are one such.
[Incidentally, when I use a makevars.win file to include these gcc options in Rcmd build etc. the problem with variable-length arrays is not flagged; maybe my command-line gcc is a different version from that in Rtools]
Well, you (and only you) can easily check that for yourself, but the other flags also matter, especially --std. Because it has been needed for the use of the MinGW headers, R on Windows is built with --std=gnu99. (Linux headers have a similar problem: using --std=c99 disables some features we test for in configure and wish to use -- and there are OS features, not language extensions.)
Murray Efford University of Otago Dunedin, New Zealand murray.eff...@otago.ac.nz<mailto:murray.eff...@otago.ac.nz> [[alternative HTML version deleted]]
Please note what the posting guide has to say about that.
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