EVAL(...) not working

following macro expanded as HELLO () while it should be "Hello World".
this piece of code is taken from http://saadahmad.ca/cc-preprocessor-metaprogramming-macro-basicsrules/

#define EMPTY() // This MACRO doesn't do anything
#define EVAL(...) __VA_ARGS__ // This is a simple identity macro
#define HELLO() "Hello World"

EVAL ( HELLO EMPTY() () )

gcc -E

# 0 "a.cpp"
# 0 "<built-in>"
# 0 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 0 "<command-line>" 2
# 1 "a.cpp"




"Hello World"

Current output:

1:
2: 
3: 
4: 
5: HELLO ( )

Variation from https://trac.cppcheck.net/ticket/15083:

#define ID(x) x
#define EXPAND(...) __VA_ARGS__
#define DO_NOTHING(_warn)
#define PROCESS(...) EXPAND(ID(DO_NOTHING)(__VA_ARGS__))

PROCESS(1 2)

Expected:

Actual:

DO_NOTHING  ( 1 2  )

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EVAL(...) not working #226

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EVAL(...) not working #226

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firewave commented on Jul 3, 2025

chrchr-github commented on Oct 6, 2026

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