This article somehow omits the 80% of both the complexity and the benefits of the GCC nested functions which makes them pointless. Namely you can cast them to function pointers and pass them e.g. as a comparator to the sort() routine. Substituting the right parent frame parameter at the time the nested function is called down the stack is tricky and requires either an explicit support in the ABI (ia-64) or an executable stack to build a trampoline or a special logic to wrap function pointers with a special but set [1].
Without all this nested functions are as useful as the "rewritten" examples in the article, one can easily do that by hand without any compiler or language support.
This problem doesn't arise with C++ lambdas because you pass them around as special objects, not as bare function pointers.
The author has been trying to push for the inclusion of nested functions into the C standard, and a lot of the resistance comes from the existence of trampolines and all of the issues that causes. His response to those issues is... to basically go "nested functions, Objective-C blocks, and C++ lambdas are all the same thing if you squint at them hard enough" and ignore all of the very real semantic differences between all of them.
For my part, I'll point out that there is one rather important difference between nested functions and C++ lambdas that the author completely ignores, as exhibited by this godbolt example: https://godbolt.org/z/35beWrrTe (note the differences in the generated assembly, especially that which cannot be explained merely by -O0 code generation).
Without all this nested functions are as useful as the "rewritten" examples in the article, one can easily do that by hand without any compiler or language support.
This problem doesn't arise with C++ lambdas because you pass them around as special objects, not as bare function pointers.
[1] https://gcc.gnu.org/onlinedocs/gccint/Trampolines.html
For my part, I'll point out that there is one rather important difference between nested functions and C++ lambdas that the author completely ignores, as exhibited by this godbolt example: https://godbolt.org/z/35beWrrTe (note the differences in the generated assembly, especially that which cannot be explained merely by -O0 code generation).
If they don't capture anything, I believe you _can_ pass them as bare function pointers.