Suppose three files are being used.

a.c:

#include "a.h"
int main(void) {}

a.h:

#include "b.h"

b.h:

extern int unused;

tendra outputs line directives based on the tokens that are present after preprocessing. Since no such tokens are found in a.h, there is no mention of a.h in the preprocessed output. This causes some configure scripts to fail. By printing the full #include stack every time the file changes, the problem is avoided. The printing is moved into a separate function because it needs to call itself recursively.

Allow literal to prefix an expression to indicate that the expression is to be interpreted as a constant expression. This is useful for offsetof, which needs to returns a target-dependent constant expression. Without a way to force an expression as a constant, offsetof cannot be used in (for example) the definitions of enumeration constants.

literal does not become a keyword by default. It must be defined using

# pragma TenDRA keyword __literal for keyword literal

where __literal can be any valid identifier.

Support anonymous unions as an extension in C. The code to handle these already exists in tendra, but is hidden in #if LANGUAGE_CPP blocks. Remove these #if blocks, add a new error so that use of this feature is still diagnosed in C by default. Add a pragma

# pragma TenDRA anonymous union ...

to allow this feature to be enabled or disabled during compilation, and default to an error for C, and no error for C++, to preserve the existing behaviour.