C++14 provided us with the option of using single quotes to separate the digits of large numeric literals. This breaks Vim's syntax highlighting.

For example, consider the following C++14 program:

#include <stdlib.h>

int main(int argc, char** argv) {
  // small numbers are fine
  int normal_number = 5;

  // large numbers have the correct highlighting but they're hard to visually parse
  int huge_number = 1000000000;

  // apostrophes help with visual parsing but mess up syntax higlighting
  int huge_number_again = 1'000'000'000;

  return EXIT_SUCCESS;

When I view this in Vim, I see the following syntax highlighting (note that I am using some additional highlighting scripts):

Vim syntax highlighting for the program described above

I would like all of the digits in huge_number_again to appear red. Is there a modification I can make to one of my syntax files or to my ~/.vimrc to correct this?

  • I see some support for C++14 was added in v7.4.923 (binary literals). But not the number separator it seems :-/ The latest C++ files from here also doesn't seem to have it yet. Commented Mar 14, 2016 at 6:17
  • 4
    For a quick fix, you can probably add syn match cNumber display contained "\d\(\d\|'\)*\(u\=l\{0,2}\|ll\=u\)\>" to ~/.vim/syntax/cpp.vim. (Btw, if that's C++, use cstdlib, not stdlib.h.)
    – muru
    Commented Mar 14, 2016 at 6:19
  • 3
    I just noticed there's an open issue since May 2014 btw. Commented Mar 14, 2016 at 6:20
  • @muru That seems to have fixed the problem. I'm fine with using a quick hack for now. Thanks!
    – Jake
    Commented Mar 14, 2016 at 6:30
  • 2
    @Carpetsmoker I am not to sure of syntax matching to know exactly what my change does. I think it will just match a digit followed any number of digits or single quotes, plus the ull fluff, but I don't know if it will match some invalid case. And apparently C++14 allows the separator in octal, binary, hex literals and floats and after the decimal point in floats. That's a lot more than I'm willing to take on.
    – muru
    Commented Mar 14, 2016 at 7:46

1 Answer 1


The vim-jp/vim-cpp repo included this change in July 2016:

syn match   cNumber     display contained "\d\('\=\d\+\)*\(u\=l\{0,2}\|ll\=u\)\>"
syn match   cNumber     display contained "0x\x\('\=\x\+\)*\(u\=l\{0,2}\|ll\=u\)\>"
syn match   cNumber     display contained "0b[01]\('\=[01]\+\)*\(u\=l\{0,2}\|ll\=u\)\>"

If you don't want to use this repo, you can add these lines to ~/.vim/syntax/cpp.vim.

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