Does "-dndebug" (lower-case) do anything in g++?

Question

I'm working on minor changes to a multi-platform C++ project with a 400-line Linux makefile that someone else created years ago.

Two lines in the makefile use -dndebug (lower-case) as a command-line argument to g++.
I think the intention was to define the ndebug symbol, but does the argument even do anything when it's lower-case?

I have minimal knowledge of g++ and make but, going by the page linked below, I think the argument needs to be upper-case to work.
http://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html

Answer 1

Yes, it should be upper case like this -DNDEBUG.

-D is the GCC option to define a macro. NDEBUG is the macro to be defined to turn off asserts as mandated by the C standard.

I have minimal knowledge of g++ and make but, going by the page linked below, I think the argument needs to be upper-case to work.

As for -dndebug, since macros are case-sensitive, I think it will not have any effect i.e. it should get ignored, unless there is some code you have that references it.

Answer 2

It's fairly easy to test:

$ cat test.cpp
#include <iostream>

int main()
{
#ifdef TEST_DEFINE
    std::cout << "defined" << std::endl;
#endif
    return 0;
}

$ g++ -o 1 -DTEST_DEFINE test.cpp
$ ./1
defined
$ g++ -o 2 -dTEST_DEFINE test.cpp
cc1plus: warning: unrecognized gcc debugging option: T [enabled by default]
cc1plus: warning: unrecognized gcc debugging option: E [enabled by default]
cc1plus: warning: unrecognized gcc debugging option: S [enabled by default]
cc1plus: warning: unrecognized gcc debugging option: T [enabled by default]
cc1plus: warning: unrecognized gcc debugging option: _ [enabled by default]
cc1plus: warning: unrecognized gcc debugging option: E [enabled by default]
cc1plus: warning: unrecognized gcc debugging option: F [enabled by default]
cc1plus: warning: unrecognized gcc debugging option: E [enabled by default]
$ ./2
$

So as you can see the -d option actually causes compiler warnings so it looks like -D is what was intended.