There is an error when compiling a c file used a nested function

Question

I have known nested functions are supported as an extension in gcc, but I compile a c file used nested function with an error. Error massage is like this:

test.cpp:6:40: error: function definition is not allowed here double
square (double z) { return z * z; }

And nested function is like this:

foo (double a, double b)
 {
  double square (double z) { return z * z; }
  return square (a) + square (b);
 }

My operation system is Mac Os, and version is 10.12.6

When I enter gcc -v in iTerm2, the response is this:

Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 9.0.0 (clang-900.0.38)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

http://en.cppreference.com/w/c/language/function_definition: *"Unlike function declaration, function definitions are allowed at file scope only (there are no nested functions)."* — UnholySheep, Dec 21 '17 at 09:29
did you use `-std=gnu11` in your compilation statement? is it `gcc`, at all? — Sourav Ghosh, Dec 21 '17 at 09:31
I'm not sure if the marked dupe is the most correct one, but it's OK. — Sourav Ghosh, Dec 21 '17 at 09:40

score 0 · Accepted Answer · answered Dec 21 '17 at 09:34

0

You're actually using using Clang, not gcc.

Notice this

Apple LLVM version 9.0.0 (clang-900.0.38)

From the clang website, Clang vs GCC (GNU Compiler Collection)

GCC supports many language extensions, some of which are not implemented by Clang. For instance, in C mode, GCC supports nested functions and has an extension allowing VLAs in structs.

answered Dec 21 '17 at 09:34

Sourav Ghosh

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Thx you all.I have just started to contact c. – tinyfeng Dec 21 '17 at 10:08

There is an error when compiling a c file used a nested function

1 Answers1