[msebor]

C17 doesn't look much different than C89. If you are used to K&R C there may be some adjustment but I would expect it to be manageable.

What might perhaps be more challenging is adjusting to the changes in compilers. They tend to optimize code more aggressively and so writing code that closely follows the rules of the language (rather than making assumptions about the underlying hardware, even valid ones) is more important today than it was back in the 80's.

[rmind]

Given the above, it is worth pointing out that the compilers are also much much better in verification and useful warnings/errors. Back in the (very old) days, there was a motivation to cut down PCC (Portable C Compiler) and give the birth to Lint as a separate application (because cutting the compilation time was a greater priority). The current trends are completely the opposite: compilers are getting increasingly more powerful built-in static analyzers and sanitizers by default.

I think the lack of powerful tools in 1990s-2000s contributed to the thought by some that C is 'diffcult' in terms of safety. However, things have moved on.

[pjmlp]

As additional info,

> Although the first edition of K&R described most of the rules that brought C's type structure to its present form, many programs written in the older, more relaxed style persisted, and so did compilers that tolerated it. To encourage people to pay more attention to the official language rules, to detect legal but suspicious constructions, and to help find interface mismatches undetectable with simple mechanisms for separate compilation, Steve Johnson adapted his pcc compiler to produce lint [Johnson 79b], which scanned a set of files and remarked on dubious constructions.

-- https://www.bell-labs.com/usr/dmr/www/chist.html