That leads to the other problem, the changes to the toolchain. Microsoft has partly addressed this issue by implementing Checked C via a fork of the well-known and widely used LLVM compiler framework. Thus, if Checked C gets traction, it'll be easy for the main LLVM project to support it.
That said, Microsoft likely chose LLVM because of its liberal licensing and it's designed to build compilers for new languages, not because it served as a vehicle to get Checked C into many hands. The older and more widely used GCC compiler would also need to support Checked C for it to enjoy greater uptake. (It goes without saying that Microsoft would likely add such support to Visual Studio if the demand manifested.)
Mozilla's Rust language has been positioned safer for writing programs normally left to C. There's little question the language has enjoyed great advances in its development and has a thriving audience. But it's still young, while C is widely and deeply entrenched. Modifying existing C apps might come at less of a cost than rewriting them entirely in Rust -- assuming Rust doesn't end up becoming everything Checked C wants to be and more.
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