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token pasting with "defined" works with gcc (cpp) but not simplecpp #218
Description
Adding this issue originally posted to the cppcheck forum per @danmar 's request.
I am using a third-party peripheral library from the manufacturer of the microprocessor that we are using, and it contains a token-pasting macro identical to the one labeled "THIS ONE" below:
#define __FOO__ 1
#define IS_DEFINED(name) (defined(__ ## name ## __)) // <--THIS ONE
#warning Before IS_DEFINED(FOO)
#if IS_DEFINED(FOO)
#warning Inside IS_DEFINED(FOO)
#endif
#warning After IS_DEFINED(FOO)
When I run cpp (Ubuntu v9.3.0) the IS_DEFINED() macro works as intended:
$ cpp ./test_token_pasting.cpp
# 1 "./test_token_pasting.cpp"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "./test_token_pasting.cpp"
./test_token_pasting.cpp:5:2: warning: #warning Before IS_DEFINED(FOO) [-Wcpp]
5 | #warning Before IS_DEFINED(FOO)
| ^~~~~~~
./test_token_pasting.cpp:8:2: warning: #warning Inside IS_DEFINED(FOO) [-Wcpp]
8 | #warning Inside IS_DEFINED(FOO)
| ^~~~~~~
./test_token_pasting.cpp:11:2: warning: #warning After IS_DEFINED(FOO) [-Wcpp]
11 | #warning After IS_DEFINED(FOO)
| ^~~~~~~
However when I run simplecpp:
$ ./simplecpp test_token_pasting.cpp
test_token_pasting.cpp:5: #warning: #warning Before IS_DEFINED(FOO)
test_token_pasting.cpp:11: #warning: #warning After IS_DEFINED(FOO)
...the IS_DEFINED() macro doesn't appear to work. Per @danmar, the specs say this macro results in undefined behavior, but it does seem to work with this version of gcc.
Activity
firewave commentedon Jul 3, 2025
Looks like a duplicate of #75.
Somehow it only prints a single line.