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ceclipseenumsincludeeclipse-cdt

Eclipse editor not showing error on functions and enum values not included

I use Eclipse CDT for a C project. I only use the editor as the build environment is outside of Eclipse.

Error markers in the code are shwon as expected with a few exceptions:

  1. When I make a function call it does not matter if the function exists or not. The editor will never show an error marker on the function call. I would expect an "Unresolved symbol" error, or similar. I would expect misspelled function names to show up as error, and I would expect existing functions that are declared in header files that I forgot to include to show up as errors. But this is not the case.

  2. When I enter the name of an enum member that does exist somewhere else (in a header file) in the project, then the editor recognizes it even if I do not include the header file where it is included. This will of course lead to a compiler error, but I would expect an error marker in the editor.

Is there some setting I am missing? Or is this just the way the eclipse editor works?

I have a faint memory of seeing those error markers long time ago, but memory may play tricks on me...

Solution

  • Resolving names whose definitions are in the project but not reachable through includes, is a known issue. It's tracked by bug 297690, and it's close to being fixed (with most of the hard work being done in bug 402498).

    Resolving the name of a function which is not in the project at all, can happen in two situations.

    In C code

    The C language does not require that functions be declared prior to their use. A use without a preceding declaration is treated as an implicit declaration.

    That is, the following C file is valid code:

    void func() {
  another_func();  // another_func is implicitly declared here
}

    The linker will try to find a matching function definition at link time, and give an error if it cannot.

    So, if you misspell another_func, the error will not be caught at compilation time (only at linking time), and similarly CDT cannot diagnose it.

    In C++ template code

    Unlike C, C++ does require that functions be declared prior to their use. However, there is one subtlety involving templates.

    If a function call occurs inside a template and some of the arguments are dependent:

    template <typename T>
void foo(T t) {
  misspelt_function(t);
}

    CDT can't diagnose the misspelt function at the point of foo's definition because of the way C++'s two-phase name lookup rules work: it would be valid to provide a definition of misspelt_function after the point of foo's definition (but before the point of instantiation) that's found by argument-dependent lookup (by being in a namespace associated with the type of t for this particular instantiation).

    (CDT could in theory diagnose the misspelt function for particular instantiations of foo, the way a compiler does, but it currently doesn't type-check the bodies of instantiations at all.)