Why is the Eclipse C++ "symbol 'std' could not be resolved" error fixed by saving the file?
I'm trying to learn how to use Eclipse for C++ development (using MinGW) and have run into an interesting problem.
While writing a simple test program I get the following error:
However simply saving the file resolves the error... Why does this happen?
After saving:
I would really like simple bugs like this to be caught without having to go and manually save the file...
I know it's really simple to just click "Save" but I know myself and I will forget and I will spend hours trying to track down a bug that isn't actually a bug. (I'm sure this will probably also happen with things other than using namespace std;.)
Answer
Eclipse's CODAN tool runs as you type, unfortunately it only parses dependencies on demand, usually with a save.
Why? Eclipse's CODAN tool isn't exactly a gazelle, so having to track through all of the file's dependencies while the user is typing is probably a system killer. This may improve with time. In the meantime, save regularly.
And, to be honest, this is probably a dodge. It should only have to search dependencies when a dependency is added. But there are a lot of buts. What about when a dependency is added to a dependency? Or a new dependency is hidden in a macro (don't do this) and hard to parse without digging through the dependencies? Or exposed by adding a define that triggers conditional compilation (I prefer different implementation files and letting the linker sort it out to conditional compilation)? What about...?
Blah. If people want to write garbage code, that's their problem. A static analyzer should focus on the needs of people who aren't trying to trick it and circumvent good style. That said, I don't know the CODAN code, and I don't know how deep one would have to go to change it to catch and handle the easy cases at a tolerable real-time rate.
But at the end of the day, the only analyzer you should pay attention to is the compiler--with the warning levels turned up to 11, of course. CODAN is not perfect. It misses and misinterprets stuff, and you may find yourself hunting a bug that's not a bug in your code. If the compiler has a bug, that's a different case, but a lot less likely. Definitely take CODAN's help, but before you spend time on an odd error, make sure it really is an error by saving and building the program.
CODAN configuring stuff:
Most of CODAN's options can be found by visiting Project->Properties on the menu and navigate the Properties dialogue to C/C++ General->Code Analysis
To turn configure CODAN's run options, to turn off updating as you type for example, go one step further to C/C++ General->Code Analysis->Launching
You will also find that if you are editing included headers in another project, you will have to force an index rebuild to to catch the modifications. Select Project->C/C++ Index->Rebuild from the menu for the project doing the including.