I'm used to this:
class Db {
_Commit(char *file, int line) {
Log("Commit called from %s:%d", file, line);
}
};
#define Commit() _Commit(__FILE__, __LINE__)
but the big problem is that I redefine the word Commit globally, and in a 400k lines application framework it's a problem. And I don't want to use a specific word like DbCommit: I dislike redundancies like db->DbCommit(), or to pass the values manually everywhere: db->Commit(__FILE__, __LINE__) is worst.
So, any advice?
So, you're looking to do logging (or something) with file & line info, and you would rather not use macros, right?
At the end of the day, it simply can't be done in C++. No matter what mechanism you chose -- be that inline functions, templates, default parameters, or something else -- if you don't use a macro, you'll simply end up with the filename & linenumber of the logging function, rather than the call point.
Use macros. This is one place where they are really not replaceable.
Even the C++ FAQ says that macros are sometimes the lesser of two evils.
As Nathon says in the comments below, in cases where you do use macros, it's best to be explicit about it. Give your macros macro-y names, like COMMIT() rather than Commit(). This will make it clear to maintainers & debuggers that there's a macro call going on, and it should help in most cases to avoid collisions. Both good things.
COMMIT() is obviously a macro call (by normal conventions) and so oughtn't to conflict with anything in your 400kloc application framework.
Wait till C++20, you cal use source_location
__builtin_FILE() in GCC.You can use a combination of default parameter and preprocessor trick to pass the caller file to a functions. It is the following:
Function declaration:
static const char *db_caller_file = CALLER_FILE;
class Db {
_Commit(const char *file = db_caller_file) {
Log("Commit called from %s", file);
}
};
Declare db_caller_file variable in the class header file.
Each translation unit will have a const char *db_caller_file. It is static, so it will not interfere between translation units. (No multiple declarations).
Now the CALLER_FILE thing, it is a macro and will be generated from gcc's command line parameters. Actually if using automated Make system, where there is generic rule for source files, it is a lot easier: You can add a rule to define macro with the file's name as a value. For example:
CFLAGS= -MMD -MF $(DEPS_DIR)/$<.d -Wall -D'CALLER_FILE="$<"'
-D defines a macro, before compiling this file.
$< is Make's substitution for the name of the prerequisite for the rule, which in this case is the name of the source file. So, each translation unit will have it's own db_caller_file variable with value a string, containing file's name.
The same idea cannot be applied for the caller line, because each call in the same translation unit should have different line numbers.
_Commit. Beginning with an underscore and having a capital letter as its second character, it is reserved for the implementation, and your using it means your program has undefined behavior._Commit, which would break your code.addr2line? In that case you could use GCC's __builtin_return_address. Logging addresses instead of names isn't pretty, but presumably you only need to know when something went wrong (which means, rarely), so that might do. The nice thing is that it "just works". I'm passing the last up-to-three callers in exceptions, which works fine (apart from being unwieldy to decipher) too.