checkedc/checkedc-clang v0.7-devbuild-2018-08-01

2018-08-01 Developer build of Checked C clang compiler

on GitHub

Summary

This is a developer build of the Checked C clang compiler. It is for use by developers who want to try out the Checked C extension while it is being implemented.

Installation Notes

Clang expects an existing C/C++ compiler before running the installer. If installing on a fresh machine, first install the C/C++ compiler. We recommend using Visual Studio 2017, which has a free Community version available. Use Visual Studio 2017's installer to ensure a C/C++ compiler and runtime are present before installing Checked C clang.

• The binaries are installers for 32-bit and 64-bit Windows versions of the compiler
• The compiler will be installed in a separate directory from your existing clang install. If you are also using the production version of clang, do not add the Checked C version to your path.

Using the compiler

See the Checked C clang users manual for directions on how to use the compiler.

To change the compiler to Checked C clang in a Visual Studio project, open the project Properties and set "Platform Toolset" to one of the "CheckedC-LLVM" versions in the drop-down. (If there are no CheckedC-LLVM options in the "Platform Toolset" dropdown, try reinstalling Checked C clang.)

Change notes

We implemented the following static checks required by the language extension:

• Validate that initializers for _Nt_checked arrays are null-terminated (issue #397)
• Check that local variables with array types or struct/union types that contain checked pointers have initializers (issue #445).
• Implement restrictions on taking address of members and variables with bounds (issue #490).

We made improvements to the Checked C header files for the C standard library:

• Add unistd_checked.h.
• Add guards to the header files (issue #293): only parse the header declarations once and don't add the checked declarations if included in a C++ file.
• Improve bounds-safe interface for strncmp. strncmp has different bounds-safe interfaces for _Nt_array_ptr and array_ptr arguments. Use the _Nt_array_ptr interface for strncmp and provide an alternate inline definition strncmp_array_ptr for the _Array_ptr interface..

We fixed the following issues:

• Build release compilers of clang for Windows installers (issue #495). The prior installers were using debug versions of the compiler.
• Fix compiler assert about bounds expression already existing (issue #537). The compiler would crash with an assert when checking a dynamic_bounds_cast whose expression argument required a bounds check.
• Fix compiler crash reported by user (issue #488). The compiler could crash after checking a bounds declaration for a function call where an argument was implicitly widened.

We made some internal changes that should not be visible externally:

• Traverse expressions during bounds declaration checking using a control-flow graph (in preparation to incorporating dataflow information during bounds declaration checking).

Extension features implemented

See the implementation roadmap and status. Some runtime checks and a lot of the static checking is not implemented yet.