I tried this test with MS compiler (cl), sun/solaris (cc) - it worked with both.
Also worked with 'gcc -std=c89' Satish On Wed, 22 May 2019, Jed Brown via petsc-dev wrote: > Agreed, though need to test that all relevant compilers error > appropriately (and that we accurately detect such errors). Satish may > remember which are most problematic. > > There are a few other --known arguments that we may need to think about. > I think these are tough: > > --known-snrm2-returns-double=0 > --known-sdot-returns-double=0 > > > Byte swapping to/from big endian for integer types can be written in a > portable way that compiles to no-op (at least when optimization is on; > but see [1]), but I don't think that's possible for floating point data. > Of course we could just compile code for both options and select which > one to call at run-time. Since they operate on arrays instead of > individual values, the dispatch should be negligible. > > [1] It's sometimes buggy. https://bugs.llvm.org/show_bug.cgi?id=41545 > > "Smith, Barry F. via petsc-dev" <[email protected]> writes: > > > It would be fantastic if we could avoid the need for the known values and > > ideally the need for batch completely!!!! > > > > This is a great idea. > > > >> On May 22, 2019, at 5:02 AM, Lisandro Dalcin via petsc-dev > >> <[email protected]> wrote: > >> > >> Barry/Satish, you know that making requests without patches is not my > >> style, but this one involves messing with BuildSystem, so please pardon me. > >> > >> I have a easy and quick proposal for compile-time determination of > >> sizeof() for the various C types. For example, in our Cray XC40, I'm > >> passing all these flags to configure to avoid the need of running with > >> batch: > >> > >> $ grep known-sizeof reconfigure-arch-gnu-opt.py > >> '--known-sizeof-MPI_Comm=4', > >> '--known-sizeof-MPI_Fint=4', > >> '--known-sizeof-char=1', > >> '--known-sizeof-double=8', > >> '--known-sizeof-float=4', > >> '--known-sizeof-int=4', > >> '--known-sizeof-long-long=8', > >> '--known-sizeof-long=8', > >> '--known-sizeof-short=2', > >> '--known-sizeof-size_t=8', > >> '--known-sizeof-void-p=8', > >> > >> > >> Look at the following two line C source, TYPE and SIZE have to be passed > >> through the preprocessor in this quick example. Defining main is of course > >> not required if we pass `-c` to the compiler. > >> > >> $ cat check-sizeof.c > >> typedef char assert_sizeof[(sizeof(TYPE)==SIZE)*2-1]; > >> int main(int arg, char *argv[]) { return 0;} > >> > >> Let's try to determine sizeof(double) by compile-time checks that do not > >> need to run the executable. > >> > >> $ cc -DTYPE=double -DSIZE=1 check-sizeof.c > >> check-sizeof.c:1:14: error: size of array ‘assert_sizeof’ is negative > >> 1 | typedef char assert_sizeof[(sizeof(TYPE)==SIZE)*2-1]; > >> | ^~~~~~~~~~~~~ > >> > >> $ cc -DTYPE=double -DSIZE=2 check-sizeof.c > >> check-sizeof.c:1:14: error: size of array ‘assert_sizeof’ is negative > >> 1 | typedef char assert_sizeof[(sizeof(TYPE)==SIZE)*2-1]; > >> | ^~~~~~~~~~~~~ > >> > >> $ cc -DTYPE=double -DSIZE=4 check-sizeof.c > >> check-sizeof.c:1:14: error: size of array ‘assert_sizeof’ is negative > >> 1 | typedef char assert_sizeof[(sizeof(TYPE)==SIZE)*2-1]; > >> | ^~~~~~~~~~~~~ > >> > >> Up to here, sizeof(double) is not 1, nor 2, nor 4. > >> > >> Let's try now if sizeof(double) is 8: > >> > >> $ cc -DTYPE=double -DSIZE=8 check-sizeof.c > >> > >> No compile error. Success! Now we know sizeof(double) is 8, we don't need > >> to run an executable, which is ideal for cross-compiling or to avoid > >> running the configure test with batch. > >> > >> > >> -- > >> Lisandro Dalcin > >> ============ > >> Research Scientist > >> Extreme Computing Research Center (ECRC) > >> King Abdullah University of Science and Technology (KAUST) > >> http://ecrc.kaust.edu.sa/ >
