clang

Customize the compilation process with Clang: Making compromises

Customize the compilation process with Clang: Making compromises

In this two-part series, we’re looking at the Clang compiler and various ways of customizing the compilation process. These articles are an expanded version of the presentation, called Merci le Compilo, which was given at CPPP in June.

In part one, we looked at specific options for customization. And, in this article, we’ll look at some examples of compromises and tradeoffs involved in different approaches.

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Customize the compilation process with Clang: Optimization options

Customize the compilation process with Clang: Optimization options

When using C++, developers generally aim to keep a high level of abstraction without sacrificing performance. That’s the famous motto “costless abstractions.” Yet the C++ language actually doesn’t give a lot of guarantees to developers in terms of performance. You can have the guarantee of copy-elision or compile-time evaluation, but key optimizations like inlining, unrolling, constant propagation or, dare I say, tail call elimination are subject to the goodwill of the standard’s best friend: the compiler.

This article focuses on the Clang compiler and the various flags it offers to customize the compilation process. I’ve tried to keep this from being a boring list, and it certainly is not an exhaustive one.

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Introduction to using libFuzzer with llvm-toolset

Introduction to using libFuzzer with llvm-toolset

“Fuzzing” an application is a great way to find bugs that may be missed by other testing methods. Fuzzers test programs by generating random string inputs and feeding them into an application. Any program that accepts arbitrary inputs from its users is a good candidate for fuzzing. This includes compilers, interpreters, web applications, JSON or YAML parsers, and many more types of programs.

libFuzzer is a library to assist with the fuzzing of applications and libraries. It is integrated into the Clang C compiler and can be enabled for your application with the addition of a compile flag and by adding a fuzzing target to your code. libFuzzer has been used successfully to find bugs in many programs, and in this article, I will show how you can integrate libFuzzer into your own applications.

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Support Lifecycle for Clang/LLVM, Go, and Rust

Support Lifecycle for Clang/LLVM, Go, and Rust

On the heels of our recently announcement, General Availability of Clang/LLVM 6.0, Go 1.10, and Rust 1.29, I want to share how we’ll be supporting them going forward. Previously, these packages had been in “Technology Preview” status, which means that they were provided for “you to test functionality and provide feedback during the development process”, and were “not fully supported under Red Hat Subscription Level Agreements, may not be functionally complete, and are not intended for production use”.

So now that we’ve promoted them to fully supported status, what does that mean? In the simplest terms, General Availability (GA) means that these packages have officially entered the “Full Support Phase” of their lifecycle:

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How to install Clang/LLVM 5 and GCC 7 on RHEL

How to install Clang/LLVM 5 and GCC 7 on RHEL

A newer version of this article is available:  How to install GCC 8 and Clang/LLVM 6 on Red Hat Enterprise Linux 7.

If you are developing with C/C++, Clang tools and newer versions of GCC can be quite helpful for checking your code and giving you better warnings and error messages to help avoid bugs. The newer compilers have better optimizations and code generation.

You can easily install the latest-supported Clang and GCC compilers for C, C++, Objective-C, and FORTRAN using yum on Red Hat Enterprise Linux.  These compilers are available as software collections that are typically updated twice a year. The May 2018 update included Clang/LLVM 5 and GCC 7.3, as well as Go and Rust.

If you want your default gcc to always be GCC 7, or you want clang to always be in your path, this article shows how to permanently enable a software collection by adding it to the profile (dot files) for your user account. A number of common questions about software collections are also answered.

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