Use @$? symbols in a C function/variable

Question

I'm curious if there's any way to use @, $, or ? in a C function or variable name. I know that linkers allow them (because of C++ name mangling).

Is there any kind of escape code that could allow this (I don't care how ugly it looks)? Or, in standard C, is this completely impossible?

[dollar sign is supported as an extension by gcc, clang and Visual Studio](http://stackoverflow.com/a/26302259/1708801) — Shafik Yaghmour, Feb 03 '15 at 18:44

Basile Starynkevitch · Accepted Answer · 2015-02-03T18:51:06.207

6

It is not possible in purely standard C.

But if using GCC (or probably Clang/LLVM) you can have $ in identifiers, and you can set the linker name using asm labels

You could perhaps also play GNU ld tricks with ld scripts.

edited Feb 03 '15 at 18:51

answered Feb 03 '15 at 18:43

Basile Starynkevitch

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Could you give an example of setting the linker name using `asm`? – MiJyn Feb 03 '15 at 18:45
I just edited my answer to link to the documentation – Basile Starynkevitch Feb 03 '15 at 18:46

score 5 · Answer 2 · answered Feb 03 '15 at 18:47

Standard C does not allow any of these (and it can't really allow ? since it's an operator and thus a separate token). GCC (and possibly compatible compilers) allow $ but not the others. However, you could use the GNU C (GCC) extension for making a declaration for an external-linkage name that references a different underlying symbol name; this may achieve what you want, e.g. if you're trying to reference C++ symbols. I believe the syntax is something like adding __asm__("symbol_name") to the end of the function declaration. There are some examples in the glibc headers on most Linux systems.

Alternatively, if you have dlsym, you could use it to look up the names at runtime.

Use @$? symbols in a C function/variable

2 Answers2