Date: Sat, 20 May 2017 13:12:08 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Ian Lepore <ian@freebsd.org> Cc: freebsd-current@freebsd.org, freebsd-toolchain@freebsd.org Subject: Re: cpp behavior? Message-ID: <20170520201208.GA33085@troutmask.apl.washington.edu> In-Reply-To: <1495301954.89384.39.camel@freebsd.org> References: <20170520000747.GA26861@troutmask.apl.washington.edu> <1495301954.89384.39.camel@freebsd.org>
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On Sat, May 20, 2017 at 11:39:14AM -0600, Ian Lepore wrote: > On Fri, 2017-05-19 at 17:07 -0700, Steve Kargl wrote: > > % which cpp > > /usr/bin/cpp > > troutmask:kargl[408] cpp --version > > FreeBSD clang version 4.0.0 (tags/RELEASE_400/final 297347) (based on > > LLVM 4.0.0) > > Target: x86_64-unknown-freebsd12.0 > > Thread model: posix > > InstalledDir: /usr/bin > > troutmask:kargl[409] cpp --help |grep trad > > -traditional-cpp Enable some traditional CPP emulation > > troutmask:kargl[410] cpp -traditional-cpp boxmuller.F90 > > cpp: error: unable to execute command: Executable "gcc" doesn't > > exist! > > > > OK, so what is the preprocessor for clang? > > > > It looks like the problem is that it sees the .F90 and wants to "do the > right thing" for fortran sources, which is "invoke gcc". I got a clue > by adding '-###' (quotes required) to see what cpp was trying to do > internally. Thanks. I did not know about the -### option. > You might get the effect you want by either adding something like -x > assembler-with-cpp, or maybe by hiding the filetype from cpp: I'm checking out the new devel/flang port (a Fortran front-end for clang). Although flang recognizes the .F90 extension, 'flang -c boxmuller.F90' dies a horrible death because it assumes a modern cpp syntax. AFAIK, the traditional syntax that gcc uses with the -traditional-cpp option is required by those who use C preprocessing directives in their Fortran. Modern cpp can corrupt valid Fortran. Having clang invoke gcc when I tried cpp caught me off guard. -- Steve 20170425 https://www.youtube.com/watch?v=VWUpyCsUKR4 20161221 https://www.youtube.com/watch?v=IbCHE-hONow
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