discrepancy between build result and Problems view in Eclipse CDT - eclipse

Question

I'm using Eclipse 4.2, with CDT, and MinGW toolchain on a Windows machine (although I've a feeling the problem has nothing to do with this specific configuration). The G++ compiler is 4.7
I'm playing with c++11 features, with the following code:
#include <iostream>
#include <iomanip>
#include <memory>
#include <vector>
#include <list>
#include <algorithm>
using namespace std;
int main( int argc, char* argv[] )
{
vector<int> v { 1, 2, 3, 4, 5, 6, 7 };
int x {5};
auto mark = remove_if( v.begin(), v.end(), [x](int n) { return n<x; } );
v.erase( mark, v.end() );
for( int x : v ) { cout << x << ", "; }
cout << endl;
}
Everything is very straight forward and idiomatic c++11. The code compiles with no problems on the command line (g++ -std=c++11 hello.cpp).
In order to make this code compile In eclipse, I set the compiler to support C++11:
Properties -> C/C++ Build -> Settings -> Miscellaneous -> Ohter Flags:
I'm adding -std=c++11
Properties -> C/C++Build -> Discovery Options -> Compiler invocation arguments:
Adding -std=c++11
That's the only change I did to either the global preferences or to the project properties.
First Question: Why do I've to change the flags in two places? When each compiler flags is used?
If I hit Ctrl-B, the project will build successfully, as expected, and running it from within eclipse show the expected result (It prints: '5, 6, 7,').
However, the editor view shows red marks of error on both the 'remove_if' line, and the 'v.erase' line. Similarly, the Problems view shows I've these two problems. Looking at the details of the problem, I get:
For the remove_if line: 'Invalid arguments. Candidates are: #0 remove_if(#0, #0, #1)
For the erase line: 'Invalid arguments Candidates are: '? erase(?), ? erase(?,?)'
Second questions: It appears there are two different builds: one for continues status, and one for the actual build. Is that right? If so, do they have different rule (compilation flags, include paths, etc.)?
Third question: In the problem details I also see: 'Name resolution problem found by the indexer'. I guess this is why the error message are so cryptic. Are those messages coming from MinGW g++ compiler or from Eclipse? What is this Name resolution? How do I fix?
Appreciate your help.
EDIT (in reply to #Eugene): Thank you Eugene. I've opened a bug on Eclipse. I think that C++11 is only partially to blame. I've cleaned my code from C++11 stuff, and removed the -std=c++11 flag from both compilation switch. And yet, the CodAn barks on the remove_if line:
int pred( int n ) { return n < 5; }
int main( int argc, char* argv[] )
{
vector<int> v;
for( int i=0; i<=7; ++i ) {
v.push_back( i );
}
vector<int>::iterator mark = remove_if( v.begin(), v.end(), pred );
v.erase( mark, v.end() );
for( vector<int>::iterator i = v.begin(); i != v.end(); ++i ) {
cout << *i << ", ";
}
cout << endl;
}
The code compiles just fine (with Ctrl-B), but CodAn doesn't like the remove_if line, saying: Invalid Arguments, Candidates are '#0 remove_if(#0,#0,#1)'.
This is a very cryptic message - it appears it misses to substitute arguments in format string (#0 for 'iterator' and #1 for 'predicate'). I'm going to update the bug.
Interestingly, using 'list' instead of 'vector' clears up the error.
However, as for my question, I'm curious about how the CodAn work. Does it uses g++ (with a customized set of flags), or another external tool (lint?), or does it do it internally in Java? If there is a tool, how can I get its command line argument, and its output?

Answer 1

Build/Settings - these flags will be included into your makefile to do actual build. Build/Discovery - these flags will be passed to a compiler when "scanner settings" are discovered by IDE. IDE will run compiler in a special mode to discover values of the predefined macros, include paths, etc.
I believe, the problems you are seeing are detected by "Codan". Codan is a static analysis built into the CDT editor, you may find its settings on "C/C++ General"/"Code Analysis". You should report the problem to the bugs.eclipse.org if you feel the errors shown are bogus. Note that CDT does not yet support all C++11 features.