llvm dev - Jun 2020 - [flang-dev] Difficulties with In-Tree Build of Flang

Hi Justin,

The flang script reads from standard input if a source file is not provided on
the command line.  It appears to hang, but it’s really just waiting for input.

Flang isn’t hooked up to a code generator yet, so instead, by default, flang
generates another Fortran source file and tries to compile that file with a
different compiler.  The default is pgf90, but you can set the environment
variable F18_FC to be a different compiler, like gfortran.

The flang script that you are running is just a throwaway driver until the real
driver is ready.  That work is under development right now, but I don’t know
when it will be ready.  Until then, we have this quirky script that lets us test
flang semantics.

- Steve

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of
"Szaday, Justin Josef via llvm-dev" <llvm-dev at lists.llvm.org>
Reply-To: "Szaday, Justin Josef" <szaday2 at illinois.edu>
Date: Wednesday, June 24, 2020 at 1:45 PM
To: "llvm-dev at lists.llvm.org" <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] [flang-dev] Difficulties with In-Tree Build of Flang

External email: Use caution opening links or attachments

Hello all,

I am having a very difficult time getting in-tree builds of Flang working. My
build commands are as follows:
cmake -G Ninja -DLLVM_ENABLE_PROJECTS="flang"
-DCMAKE_INSTALL_PREFIX=$(pwd) -DCMAKE_BUILD_TYPE=MinSizeRel ../llvm
cmake --build . --target check-flang
cmake --build . --target install

The build itself completes successfully, and all the Flang tests pass when using
“check-flang”; however, “flang -v” and “flang -h” hang (it does not produce any
output and has to be killed) and, when trying to compile a program, I get the
error message “execvp(pgf90) failed: No such file or directory” (which fails
even if I set F18_FC to gfortran or flang). I have tried building it on a few
machines to no avail. I have tested both the Debug and MinSizeRel build types,
used both Ninja and Unix Makefiles to build it, and tested a few different
versions of GCC/G++, ultimately settling on v9.1.0. I am building from master of
the llvm-project GitHub repository.

Any insights here would be appreciated, I am at a loss about what else to try
here. Any other debugging suggestions or usage tips would be appreciated as
well.

Thanks,
Justin

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