9554152c8a
A check for character substrings masquerading as array sections was using expression analyzer on the array base. When this array happened to be an assumed-size array, the analyzer emitted a semantic error that did not correspond to any issue with the source code. To avoid that, check whether the object is an assumed-size array before using the expression analyzer on it. While at it, replace the call to GetShape with a simple check for rank, since that's the only information needed. Fixes https://github.com/llvm/llvm-project/issues/150297 (cherry picked from commit 8fcbd06b25fd0c1b4bc4a4c8775129f7dab1affd)
Flang
Flang is a ground-up implementation of a Fortran front end written in modern C++. It started off as the f18 project (https://github.com/flang-compiler/f18) with an aim to replace the previous flang project (https://github.com/flang-compiler/flang) and address its various deficiencies. F18 was subsequently accepted into the LLVM project and rechristened as Flang.
Please note that flang is not ready yet for production usage.
Getting Started
Read more about flang in the docs directory. Start with the compiler overview.
To better understand Fortran as a language and the specific grammar accepted by flang, read Fortran For C Programmers and flang's specifications of the Fortran grammar and the OpenMP grammar.
Treatment of language extensions is covered in this document.
To understand the compilers handling of intrinsics, see the discussion of intrinsics.
To understand how a flang program communicates with libraries at runtime, see the discussion of runtime descriptors.
If you're interested in contributing to the compiler, read the style guide and also review how flang uses modern C++ features.
If you are interested in writing new documentation, follow LLVM's Markdown style guide.
Consult the Getting Started with Flang for information on building and running flang.