Header-only mode still includes cassert, causing assert macro to be defined.

[toojays]

Consider the following example:

#define FMT_HEADER_ONLY
#include <fmt/format.h>
//#undef assert

struct Test
{
    void assert (bool pass, const char *test_name)
    {
        fmt::print("{}: {}", test_name, pass ? "PASS" : "FAIL");
    }
};

int main()
{
    Test test;
    test.assert(true, "mumble");
    return 0;
}

It fails compilation (godbolt) with:

<source>:7:50: error: macro "assert" passed 2 arguments, but takes just 1
    7 |     void assert (bool pass, const char *test_name)
      |                                                  ^
In file included from /opt/compiler-explorer/gcc-10.2.0/include/c++/10.2.0/cassert:44,
                 from /opt/compiler-explorer/libs/fmt/trunk/include/fmt/format-inl.h:12,
                 from /opt/compiler-explorer/libs/fmt/trunk/include/fmt/format.h:4230,
                 from <source>:2:
/usr/include/assert.h:92: note: macro "assert" defined here
   92 | #  define assert(expr)       \
      | 
<source>:16:31: error: macro "assert" passed 2 arguments, but takes just 1
   16 |     test.assert(true, "mumble");
      |                               ^
In file included from /opt/compiler-explorer/gcc-10.2.0/include/c++/10.2.0/cassert:44,
                 from /opt/compiler-explorer/libs/fmt/trunk/include/fmt/format-inl.h:12,
                 from /opt/compiler-explorer/libs/fmt/trunk/include/fmt/format.h:4230,
                 from <source>:2:
/usr/include/assert.h:92: note: macro "assert" defined here
   92 | #  define assert(expr)       \
      | 
<source>:7:10: error: variable or field 'assert' declared void
    7 |     void assert (bool pass, const char *test_name)
      |          ^~~~~~
<source>:10:5: error: expected ';' at end of member declaration
   10 |     }
      |     ^
      |      ;
<source>: In function 'int main()':
<source>:16:10: error: 'struct Test' has no member named 'assert'
   16 |     test.assert(true, "mumble");
      |          ^~~~~~

As a workaround we can #undef assert immediately after including format.h.

It looks like some work was done to remove the dependency on cassert in 2f9acd1, but this did not extend to the header only mode?

Is it just a matter of replacing the remaining assert() calls with FMT_ASSERT()?

[vitaut]

Removing the assert dependency from the implementation is a non-goal but I'm open to a PR that replaces it with FMT_ASSERT.