[flang] [llvm] [flang] Add HOSTNM runtime and lowering intrinsics implementation (PR #131910)

[via llvm-commits]

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@@ -0,0 +1,60 @@
+! REQUIRES: system-linux
+
+! Verify that the hostname obtained by HOSTNM() intrinsic is the same
+! as the hostname obtained by directly calling C gethostname().
+
+! RUN: %flang -L"%libdir" %s -o %t
+! RUN: env LD_LIBRARY_PATH="$LD_LIBRARY_PATH:%libdir" %t | FileCheck %s
+
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jeanPerier wrote:

You cannot add end-to-end executable tests to LIT.
LIT are supposed small regression test that exercise a limited portion of the compilation pipeline.
Typically lowering tests will check for the generated output of `-emit-hlfir`.

You can typically generate these tests expected output using https://github.com/llvm/llvm-project/blob/main/mlir/utils/generate-test-checks.py script, and pruning things unrelated to the tests (also beware to remove fragile things like the file name constant name and size that are passed to the Hostnm runtime call. They will depend on where the llvm source directory of the build is and are not portable). 

I also find it a bit frustrating, but if you want to add end-to-end tests for LLVM, this has to be done in another repo: https://github.com/llvm/llvm-test-suite/tree/main/Fortran/UnitTests

The idea is that lowering lit test should exercise flang code, and not the assembler/linker/os/c runtime... so that a failure in these tests points to a failure in them should point to an issue in code-generation and not an issue with the target OS libraries. It also makes them more portable.

See https://llvm.org/docs/TestingGuide.html#quick-start

https://github.com/llvm/llvm-project/pull/131910