EmacsTags + CompanyMode and you should be good to go. You'll need to install the correct tags package for your system, but it's only about 10 minutes of minor annoyance.
Whenever the point is over a word in a C++ codebase, e.g. FooSystem, it will be underlined, and you can click on it and jump to definition, show all references, etc. Then if you type Foo, CompanyMode should pop up a dialog box that will autocomplete FooManager.
I think you can also install a fuzzy matching package for CompanyMode which allows you to type e.g. "FSy" to complete "FooSystem", though I may be confusing Helm and CompanyMode.
You may also want to check out the Projectile package. It's for large project navigation, and I think it helps with automatically running ETags / GTags on an as-needed basis.
Whenever the point is over a word in a C++ codebase, e.g. FooSystem, it will be underlined, and you can click on it and jump to definition, show all references, etc. Then if you type Foo, CompanyMode should pop up a dialog box that will autocomplete FooManager.
I think you can also install a fuzzy matching package for CompanyMode which allows you to type e.g. "FSy" to complete "FooSystem", though I may be confusing Helm and CompanyMode.
You may also want to check out the Projectile package. It's for large project navigation, and I think it helps with automatically running ETags / GTags on an as-needed basis.