I'm trying to use Eclipse to edit sources, compiled under C++ Builder, but stuck with Unresolved inclusion problem.
For example, code like:
#include <vector>
Gives Unresolved inclusion: <vector> error in Eclipse IDE. C++ Builder indeed has no vector file, instead it has vector.h which is used by compiler.
Eclipse IDE gives no error if I write
#include <vector.h>
How do I tell Eclipse to use vector.h when it sees #include <vector>?
This allowed me to avoid Eclipse "Unresolved inclusion" error.
In my case I had to find the location of the C++ vector header on my computer (which is a Mac):
find /usr/local -name vector -print
I found the correct include location in folder "/usr/include/c++/4.2.1". Then I set my project eclipse settings like so:
Project->Properties->C/C++ General->Paths and Symbols->GNU C++->(Add)->"/usr/include/c++/4.2.1"
I'm not using C++ Builder, but my solution might address part of your trouble.
You could also try use "CDT GCC Built-in Compiler Settings". Go to the project properties > C/C++ General > Preprocessor Include Path > Providers tab
then check "CDT GCC Built-in Compiler Settings" if it is not.
None of the other solutions (play with include path, etc) worked for me for the type 'string', but this one fixed it.
On Windows, with Eclipse CDT Oxygen, none of the solutions described here worked for me (including the "Provider" - "CDT GCC Built-in Compiler Settings").
What works for me is:
Install Cygwin, with notably the following packages (maybe not all are strictly needed for this):
libgcc1
cygwin32-gcc-core, cygwin32-gcc-g++
gcc-g++
mingw64-x86_64-gcc-core, mingw64-x86_64-gcc-g++
In Project Properties:
Go to "C/C++ Build" - "Tool Chain Editor" and select "Cygwin GCC" as the "Current toolchain":
Go to "C/C++ General" - "Preprocessor Include Paths, Macors etc.", in the "Providers" tab, select:
"CDT Users Setting Entries" (I need them for other includes, such as the Google Test ones, which I manually referenced);
"CDT GCC Built-in Compiler Settings Cygwin".
memory and memory.h don't refer to the same source.
One is for c, the other for c++
Do you have the right includes source in your project settings ?
Related
The error is as above. I have what should be all the necessary files include in the eclipse project:
/usr/include/c++/4.6
/usr/include
/usr/include/linux
/usr/local/include
etc.
I tried std::cout and using namespace std; cout but it still says unresolved.
I have imported iostream and cstdlib.
Also, I'm on Ubuntu 12.04 with eclipse 3.7.2.
Code snippet:
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include "XPLMDisplay.h"
#include "XPLMGraphics.h"
int XPluginStart(char * outName, char * outSig, char * outDesc) {
/* ... */
std::cout << "test" << std::endl;
/* ... */
}
using namespace std;
UPDATE: I had created the eclipse project from existing code. Creating a new c++ project fixes it. I'll accept an answer that explains what setting in the existing project could cause this (so I don't have to cut & paste all my projects).
Most likely you have some system-specific include directories missing in your settings which makes it impossible for indexer to correctly parse iostream, thus the errors. Selecting Index -> Search For Unresolved Includes in the context menu of the project will give you the list of unresolved includes which you can search in /usr/include and add containing directories to C++ Include Paths and Symbols in Project Properties.
On my system I had to add /usr/include/c++/4.6/x86_64-linux-gnu for bits/c++config.h to be resolved and a few more directories.
Don't forget to rebuild the index (Index -> Rebuild) after adding include directories.
To get rid of symbol warnings you don't want, first you should understand how Eclipse CDT normally comes up with unknown symbol warnings in the first place. This is its process, more or less:
Eclipse detects the GCC toolchains available on the system
Your Eclipse project is configured to use a particular toolchain
Eclipse does discovery on the toolchain to find its include paths and built-in defines, i.e. by running it with relevant options and reading the output
Eclipse reads the header files from the include paths
Eclipse indexes the source code in your project
Eclipse shows warnings about unresolved symbols in the editor
It might be better in the long run to fix problems with the earlier steps rather than to override their results by manually adding include directories, symbols, etc.
Toolchains
If you have GCC installed, and Eclipse has detected it, it should list that GCC as a toolchain choice that a new C++ project could use, which will also show up in Window -> Preferences -> C/C++ -> New CDT Project Wizard on the Preferred Toolchains tab's Toolchains box on the right side. If it's not showing up, see the CDT FAQ's answer about compilers that need special environments (as well as MinGW and Cygwin answers for the Windows folk.)
If you have an existing Eclipse C++ project, you can change the associated toolchain by opening the project properties, and going to C/C++ Build -> Tool Chain Editor and choosing the toolchain you want from the Current toolchain: pulldown. (You'll have to uncheck the Display compatible toolchains only box first if the toolchain you want is different enough from the one that was previously set in the project.)
If you added a toolchain to the system after launching Eclipse, you will need to restart it for it to detect the toolchain.
Discovery
Then, if the project's C/C++ Build -> Discovery Options -> Discovery profiles scope is set to Per Language, during the next build the new toolchain associated with the project will be used for auto-discovery of include paths and symbols, and will be used to update the "built-in" paths and symbols that show up in the project's C/C++ General -> Paths and Symbols in the Includes and Symbols tabs.
Indexing
Sometimes you need to re-index again after setting the toolchain and doing a build to get the old symbol warnings to go away; right-click on the project folder and go to Index -> Rebuild to do it.
(tested with Eclipse 3.7.2 / CDT 8)
Thanks loads for the answers above. I'm adding an answer for a specific use-case...
On a project with two target architectures each with its own build configuration (the main target is an embedded AVR platform; the second target is my local Linux PC for running unit tests) I found it necessary to set Preferences -> C/C++ -> Indexer -> Use active build configuration as well as to add /usr/include/c++/4.7, /usr/include and /usr/include/c++/4.7/x86_64-linux-gnu to Project Properties -> C/C++ General -> Paths and Symbols and then to rebuild the index.
I tried the marked solution here first. It worked but it is kind hacky, and you need to redo it every time you update the gcc. I finally find a better solution by doing the followings:
Project -> Properties -> C/C++ General -> Preprocessor Include Paths, Macros, etc.
Providers -> CDT GCC built-in compiler settings
Uncheck Use global provider shared between projects (you can also modify the global provider if it fits your need)
In Command to get compiler specs, add -std=c++11 at the end
Index->Rebuild
Voila, easy and simple. Hopefully this helps.
Note: I am on Kepler. I am not sure if this works on earlier Eclipse.
I am using Ubuntu 12.04 / Eclipse 4.2.1 / CDT 8.1.1 and I used to have the same problem for quite some time: importing a C++ project from SVN would cause these annoying "Unresolved inclusion" errors and I would instead have to create a new project and copy the files in there as a work-around (still partial, since SVN functionality would not be there!).
At last, I have just found a simple, satisfactory solution:
Go to Project -> Properties -> C/C++ General -> Preprocessor Include Paths, Macros etc. -> Providers and check Enable language settings providers for this project.
Restart Eclipse.
Hopefully that already does the trick.
I had a similar problem with *std::shared_ptr* with Eclipse using MinGW and gcc 4.8.1. No matter what, Eclipse would not resolve *shared_ptr*. To fix this, I manually added the __cplusplus macro to the C++ symbols and - viola! - Eclipse can find it. Since I specified -std=c++11 as a compile option, I (ahem) assumed that the Eclipse code analyzer would use that option as well. So, to fix this:
Project Context -> C/C++ General -> Paths and Symbols -> Symbols Tab
Select C++ in the Languages panel.
Add symbol __cplusplus with a value of 201103.
The only problem with this is that gcc will complain that the symbol is already defined(!) but the compile will complete as before.
For me it helped to enable the automated discovery in Properties -> C/C++-Build -> Discovery Options to resolve this problem.
I simply delete all error in the buttom: problem list.
then close project
and reopen project
clean project
build all
run
then those stupids errors go.
If all else fails, like it did in my case, then just disable annotations. I started a c++11 project with own makefile but couldn't fix all the problems. Even if you disable annotations, eclipse will still be able to help you do some autocompletion. Most importantly, the debugger still works!
I had the same issue using Eclipse CDT (Kepler) on Windows with Cygwin installed. After pointing the project properties at every Cygwin include I could think of, it still couldn't find cout.
The final missing piece turned out to be C:cygwin64\lib\gcc\x86_64-pc-cygwin\4.8.2\install-tool\include.
To sum up:
Right click on the project
Choose Properties
Navigate to C/C++ General > Paths and Symbols > Includes tab
Click Add...
Click File system...
Browse to the location of your Cygwin lib\gcc\x86_64-pc-cygwin\4.8.2\install-tool\include
Click OK
Here is what my project includes ended up looking like when it was all said and done:
You guys are looking under the wrong section.
I realized the difference when I installed in Linux after recently getting frustrated with Windows and the difference was immediately apparent.
In the new setup I have an includes folder in a projected that I created out of existing source. I can expand this and see a ton of includes; however, I cannot add to them.
This lead me to a hunt for where these files were being listed.
They're listed under the Project Properties > C/C++ General > Preprocessor Includes > GNU C++
CDT GCC Built-in Compiler Settings [Shared]
Under that is a ton of includes.
These settings are set by the toolchain you've selected.
I have created the Makefile project using cmake on Ubuntu 16.04.
When created the eclipse project for the Makefiles which cmake generated I created the new project like so:
File --> new --> Makefile project with existing code.
Only after couple of times doing that I have noticed that the default setting for the "Toolchain for indexer settings" is none.
In my case I have changed it to Linux GCC and all the errors disappeared.
Hope it helps and let me know if it is not a legit solution.
Cheers,
Guy.
I had this happen after updating gcc and eclipse on ArchLinux. What solved it for me was Project -> C/C++ Index -> Rebuild.
Just adding yet another bit of advice after trying a bunch of stuff myself and it not working....
I had GCC installed and the path to the includes set correctly. Had the std error as well, and couldn't get anything working for cout (and I suspect anything in the SL...)
Took me awhile to realize that g++ wasn't installed - gcc was but not g++. So just do:
sudo apt-get install g++
Restart eclipse. Assuming above mentioned details about gcc & paths to includes are fine, you should be okay now...
mine was bit easy to fig out right click >run as>run configration
check boxes include system lib,inherited mains
I have a Windows8 machine with mingw installed in c:\mingw
Eclipse does successfully compile programs, but it considers lines to contain errors that are fine when compiled. Eclipse is not finding the libraries itself.
When I first build a project in eclipse with the CDT components install, it shows errors on every #include and every line using an object.
Example:
#include <iostream>
using namespace std;
int main() {
cout << "hello\n";
}
The above code shows errors on the include, the using and the cout << line.
I can get rid of the errors by clicking:
project->properties C++/General Preprocessor Include
Then on the providers tab, I can check off "CDT Build output parser" and fix the mistakes as described by the first answer below, which I am upchecking. But this only works for the project. I have to do this every time. How can I get eclipse to simply accept standard C++ EVERY TIME I build a new project without reconfiguring each project?
I have been able to stop errors on the includes by going into project settings and adding the directories:
c:/bin/mingw/lib/gcc/include
...
That leaves the errors on lines using the objects.
#include <iostream>
#include <string>
#include <regex>
using namespace std;
int main() {
string s = "this is a test.";
regex e("est");
smatch m;
The line with regex still shows an error: "type regex could not be resolved"
even though the code compiles and the regex include is recognized.
Additionally, on a different machine running windows 8.1 with Mingw installed, eclipse will not debug. Is there some document on how to connect Eclipse CDT to the library?
While you obviously successfully compile the code with gcc from within Eclipse, Eclipse has its own built-in C++ parser and you need to separately let it know that you are using C++11.
Add the -std=c++11 option to the CDT GCC Builtin Compiler Settings under Project propierties -> C/C++ General -> Preprocessor Include Paths, the compiler specs should look similar to this:
${COMMAND} -E -P -v -dD ${INPUTS} -std=c++11
UPDATE. Please read Setting Up Include Paths and Macros for C/C++ Indexer to understand how CDT automatic discovery of include paths and preprocessor symbols (aka Scanner Discovery) for supported tool chains is applicable to you.
The gist is that the CDT uses the Language Settings Providers to find include paths and preprocessor symbols. And Language Settings Providers can be configured on project properties page "Preprocessor Include Paths, Macros, etc."
Once you have proper settings you can make them a template workspace and just copy the template workspace over for your new projects, or alternatively have a script that will set up just the relevant settings. Also see: Setting preferences for all Eclipse workspaces.
I have had the same problem. Eclipse underlined like an error a regex keyword, but project was built without errors. I chose a Language Dialect as "ISO C++1y (-std=c++1y)" in Properties->C/C++ Build->GCC C++ Compiler->Dialect Language Standart
Been a while, but adding in case someone else finds this answer as I did.
I had what appeared to be this issue but it turned out that while I had installed MinGW, eclipse still expected me to have installed cygwin. Go to project properties > C/C++ Build > Tool Chain Editor > Current Toolchain and select the appropriate option.
Not sure why it defaults the setting to a toolchain it can't find.
Since I upgraded from Eclipse Indigo to Juno (on Ubuntu 12.04), I've been having the problem where it shows "unresolved inclusion" errors for standard libraries (e.g. next to #include <iostream> and #include <vector>, etc.), although the program builds and runs fine (using g++). This only occurs in new projects created with Juno, not old ones from Indigo in my workspace.
Thanks to several other SO questions (see below*), I was able to trace the source of the problem to the absence of the "built-in values" in a project's Properties > C/C++ General > Paths and Symbols > Includes tab:
/usr/include/c++/4.6
/usr/include/c++/4.6/x86_64-linux-gnu
/usr/include/c++/4.6/backward
/usr/lib/gcc/x86_64-linux-gnu/4.6/include
/usr/lib/gcc/x86_64-linux-gnu/4.6/include-fixed
/usr/include/x86_64-linux-gnu
/usr/include
are present when the "Show built-in values" checkbox is ticked in my old Indigo projects that didn't have this problem, but are absent in my new projects created with Juno. Sure enough, if I add these seven directories manually to the Includes tab in a project's settings, the problem disappears. But I don't want to have to do this manually for every new project I create. Is there a reason this is no longer the default in Juno, and is there a way to restore it?
*Other SO questions with similar issues I have consulted but did not solve my problem:
Eclipse 3.7.0 Indigo with CDT shows many false compilation errors: I thought Erzsébet Geréb's answer would be my solution -- in Juno, if I create a new C++ project with "Project type" as one of the categories under "GNU Autotools" instead of "Executable," the built-in directories are there. (In Indigo, there's no GNU Autotools category. If I created it in Indigo as an empty or Hello World project under "Executable," those directories are there, but they're not if I do it that way in Juno -- I have to pick an option under "GNU Autotools.") But then, with a "GNU Autotools" project, when I go to the project's Properties > C/C++ Build > Settings, the "Tool Settings" tab is no longer present and I am unable to add include paths for the GCC C++ Compiler and libraries for the GCC C++ Linker, which I need to do because many of my C++ projects use OpenCV libraries.
"Unresolved inclusion" error with Eclipse CDT for C standard library headers: Told me how to add the include paths manually, but not how to have the built-in ones added by default
error , Symbol 'vector' could not be resolved: Cleaning ~/.eclipse/ and rebuilding index didn't help.
Eclipse CDT Builtin Include Directories: Discovery Options are set the same as my projects that do work properly.
eclipse CDT 8.01 - default paths (libstdc,libstdc++) totally disappeared in 'includes' directory
Eclipse CDT indexer lost after system update: Doesn't solve the problem for all new projects.
Please
Open the Eclipse Preferences dialog (Windows | Preferences).
Open C++ | Build | Settings.
Open the Discovery tab.
Select the built-in compiler settings entry.
Press the Clear Entries button.
Afterwards eclipse should request the defaults again from the compiler.
On Arch Linux I had to do this after each GCC version change, because in that case the locations for the defaults changed as the version is encoded in the folder name, and eclipse does not notice this.
FWIW:
I found that after importing a project from another computer, I was not getting any thing showing up under the "Includes" section of my project in the Project Explorer. To fix this, I needed to delete the folder /workspace/project/.settings/. For me it only had one file (language.settings.xml).
Then everything was back to normal.
The error is as above. I have what should be all the necessary files include in the eclipse project:
/usr/include/c++/4.6
/usr/include
/usr/include/linux
/usr/local/include
etc.
I tried std::cout and using namespace std; cout but it still says unresolved.
I have imported iostream and cstdlib.
Also, I'm on Ubuntu 12.04 with eclipse 3.7.2.
Code snippet:
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include "XPLMDisplay.h"
#include "XPLMGraphics.h"
int XPluginStart(char * outName, char * outSig, char * outDesc) {
/* ... */
std::cout << "test" << std::endl;
/* ... */
}
using namespace std;
UPDATE: I had created the eclipse project from existing code. Creating a new c++ project fixes it. I'll accept an answer that explains what setting in the existing project could cause this (so I don't have to cut & paste all my projects).
Most likely you have some system-specific include directories missing in your settings which makes it impossible for indexer to correctly parse iostream, thus the errors. Selecting Index -> Search For Unresolved Includes in the context menu of the project will give you the list of unresolved includes which you can search in /usr/include and add containing directories to C++ Include Paths and Symbols in Project Properties.
On my system I had to add /usr/include/c++/4.6/x86_64-linux-gnu for bits/c++config.h to be resolved and a few more directories.
Don't forget to rebuild the index (Index -> Rebuild) after adding include directories.
To get rid of symbol warnings you don't want, first you should understand how Eclipse CDT normally comes up with unknown symbol warnings in the first place. This is its process, more or less:
Eclipse detects the GCC toolchains available on the system
Your Eclipse project is configured to use a particular toolchain
Eclipse does discovery on the toolchain to find its include paths and built-in defines, i.e. by running it with relevant options and reading the output
Eclipse reads the header files from the include paths
Eclipse indexes the source code in your project
Eclipse shows warnings about unresolved symbols in the editor
It might be better in the long run to fix problems with the earlier steps rather than to override their results by manually adding include directories, symbols, etc.
Toolchains
If you have GCC installed, and Eclipse has detected it, it should list that GCC as a toolchain choice that a new C++ project could use, which will also show up in Window -> Preferences -> C/C++ -> New CDT Project Wizard on the Preferred Toolchains tab's Toolchains box on the right side. If it's not showing up, see the CDT FAQ's answer about compilers that need special environments (as well as MinGW and Cygwin answers for the Windows folk.)
If you have an existing Eclipse C++ project, you can change the associated toolchain by opening the project properties, and going to C/C++ Build -> Tool Chain Editor and choosing the toolchain you want from the Current toolchain: pulldown. (You'll have to uncheck the Display compatible toolchains only box first if the toolchain you want is different enough from the one that was previously set in the project.)
If you added a toolchain to the system after launching Eclipse, you will need to restart it for it to detect the toolchain.
Discovery
Then, if the project's C/C++ Build -> Discovery Options -> Discovery profiles scope is set to Per Language, during the next build the new toolchain associated with the project will be used for auto-discovery of include paths and symbols, and will be used to update the "built-in" paths and symbols that show up in the project's C/C++ General -> Paths and Symbols in the Includes and Symbols tabs.
Indexing
Sometimes you need to re-index again after setting the toolchain and doing a build to get the old symbol warnings to go away; right-click on the project folder and go to Index -> Rebuild to do it.
(tested with Eclipse 3.7.2 / CDT 8)
Thanks loads for the answers above. I'm adding an answer for a specific use-case...
On a project with two target architectures each with its own build configuration (the main target is an embedded AVR platform; the second target is my local Linux PC for running unit tests) I found it necessary to set Preferences -> C/C++ -> Indexer -> Use active build configuration as well as to add /usr/include/c++/4.7, /usr/include and /usr/include/c++/4.7/x86_64-linux-gnu to Project Properties -> C/C++ General -> Paths and Symbols and then to rebuild the index.
I tried the marked solution here first. It worked but it is kind hacky, and you need to redo it every time you update the gcc. I finally find a better solution by doing the followings:
Project -> Properties -> C/C++ General -> Preprocessor Include Paths, Macros, etc.
Providers -> CDT GCC built-in compiler settings
Uncheck Use global provider shared between projects (you can also modify the global provider if it fits your need)
In Command to get compiler specs, add -std=c++11 at the end
Index->Rebuild
Voila, easy and simple. Hopefully this helps.
Note: I am on Kepler. I am not sure if this works on earlier Eclipse.
I am using Ubuntu 12.04 / Eclipse 4.2.1 / CDT 8.1.1 and I used to have the same problem for quite some time: importing a C++ project from SVN would cause these annoying "Unresolved inclusion" errors and I would instead have to create a new project and copy the files in there as a work-around (still partial, since SVN functionality would not be there!).
At last, I have just found a simple, satisfactory solution:
Go to Project -> Properties -> C/C++ General -> Preprocessor Include Paths, Macros etc. -> Providers and check Enable language settings providers for this project.
Restart Eclipse.
Hopefully that already does the trick.
I had a similar problem with *std::shared_ptr* with Eclipse using MinGW and gcc 4.8.1. No matter what, Eclipse would not resolve *shared_ptr*. To fix this, I manually added the __cplusplus macro to the C++ symbols and - viola! - Eclipse can find it. Since I specified -std=c++11 as a compile option, I (ahem) assumed that the Eclipse code analyzer would use that option as well. So, to fix this:
Project Context -> C/C++ General -> Paths and Symbols -> Symbols Tab
Select C++ in the Languages panel.
Add symbol __cplusplus with a value of 201103.
The only problem with this is that gcc will complain that the symbol is already defined(!) but the compile will complete as before.
For me it helped to enable the automated discovery in Properties -> C/C++-Build -> Discovery Options to resolve this problem.
I simply delete all error in the buttom: problem list.
then close project
and reopen project
clean project
build all
run
then those stupids errors go.
If all else fails, like it did in my case, then just disable annotations. I started a c++11 project with own makefile but couldn't fix all the problems. Even if you disable annotations, eclipse will still be able to help you do some autocompletion. Most importantly, the debugger still works!
I had the same issue using Eclipse CDT (Kepler) on Windows with Cygwin installed. After pointing the project properties at every Cygwin include I could think of, it still couldn't find cout.
The final missing piece turned out to be C:cygwin64\lib\gcc\x86_64-pc-cygwin\4.8.2\install-tool\include.
To sum up:
Right click on the project
Choose Properties
Navigate to C/C++ General > Paths and Symbols > Includes tab
Click Add...
Click File system...
Browse to the location of your Cygwin lib\gcc\x86_64-pc-cygwin\4.8.2\install-tool\include
Click OK
Here is what my project includes ended up looking like when it was all said and done:
You guys are looking under the wrong section.
I realized the difference when I installed in Linux after recently getting frustrated with Windows and the difference was immediately apparent.
In the new setup I have an includes folder in a projected that I created out of existing source. I can expand this and see a ton of includes; however, I cannot add to them.
This lead me to a hunt for where these files were being listed.
They're listed under the Project Properties > C/C++ General > Preprocessor Includes > GNU C++
CDT GCC Built-in Compiler Settings [Shared]
Under that is a ton of includes.
These settings are set by the toolchain you've selected.
I have created the Makefile project using cmake on Ubuntu 16.04.
When created the eclipse project for the Makefiles which cmake generated I created the new project like so:
File --> new --> Makefile project with existing code.
Only after couple of times doing that I have noticed that the default setting for the "Toolchain for indexer settings" is none.
In my case I have changed it to Linux GCC and all the errors disappeared.
Hope it helps and let me know if it is not a legit solution.
Cheers,
Guy.
I had this happen after updating gcc and eclipse on ArchLinux. What solved it for me was Project -> C/C++ Index -> Rebuild.
Just adding yet another bit of advice after trying a bunch of stuff myself and it not working....
I had GCC installed and the path to the includes set correctly. Had the std error as well, and couldn't get anything working for cout (and I suspect anything in the SL...)
Took me awhile to realize that g++ wasn't installed - gcc was but not g++. So just do:
sudo apt-get install g++
Restart eclipse. Assuming above mentioned details about gcc & paths to includes are fine, you should be okay now...
mine was bit easy to fig out right click >run as>run configration
check boxes include system lib,inherited mains
I am getting this error in the TestExecute.cpp -
"Symbol 'std' could not be resolved"
CODE
#include <iostream>
using namespace std;
I just created a executable project in Eclipse (in Windows 7) as shown below. It seems like I am selecting a toolchain that is not supported. Is it so? I have installed Cygwin and it is available in preferences.
EDIT: Based on #RobertoWilko comment, removing the line "using namespace std;
" removed the error. But the binary is not created. "Launch Failed. Binary not found". How to correct this?
Try out this step: https://www.eclipse.org/forums/index.php/t/636348/
Go to
Project -> Properties -> C/C++ General -> Preprocessor Include Paths, Macros, etc. -> Providers
Activate CDT GCC Built-in Compiler Settings
Deactivate Use global provider shared between projects
Add the command line argument -std=c++11.
I do not know whether you have solved this problem but I want to post my solution for those might ran into the same problem.
First, make sure that you have the "Includes" folder in your Project Explorer. If you do not have it, go to second step. If you have it, go to third step.
Second, Window -> Preferences-> C/C++- > Build >Environment: Create two environment variables:
a) Name: C_INCLUDE_PATH Value: /usr/include
b) Name: CPLUS_INCLUDE_PATH Value: /usr/include/c++
Go to Cygwin/usr/include/, if you cannot find folder "c++", copy it from \cygwin\lib\gcc\i686-pc-cygwin\X.X.X\include and Then restart your Eclipse.
Third, Right Click your project in Project Explorer -> Properties -> C/C++ General -> Paths and Symbols -> Includes -> Languages:GNU C++
If you can find some C++ folders in the "Include directories" then click Apply and OK. Change a bit your codes, and save it.
You will find there will be not symbol could not be resolved problems.
I documented my solution, hoping someone might get benefits.
You can rewrite the code likes this:
#include<iostream>
#include<stdio.h>
using namespace std;
For MinGW this worked for me:
Right click project, select Properties
Go to C/C++ General - Paths and Symbols - Includes - GNU C++ - Include directories
Select Add...
Select Variables...
Select MINGW_HOME and click OK
Click Apply and OK
You should now see several MinGW paths in Includes in your project explorer.
The errors may not disappear instantly, you may need to refresh/build your project.
If you are using Cygwin, there could be an equivalent variable present.
The includes folder in the project is probably missing /usr/include/c++.
Goto your project in project explorer, right click -> Properties -> C\C++ Build -> Environment -> add -> value= /usr/include/c++. Restart eclipse.
What allowed me to fix the problem was going to: Project -> Properties -> C/C++ General -> Preprocessor Include Paths, Macros, etc. -> Providers -> CDT GCC built-in compiler settings, enabling that and disabling the CDT Cross GCC Built-in Compiler Settings
Install C++ SDK:
Help > Install New Software > Work with: path for your eclipse version > search for C++ and install C++ sdk development tools.
Example for a path: Mars - http://download.eclipse.org/releases/mars
I was having this problem using Eclipse Neon on Kubuntu with a 16.04 kernel, I had to change my #include <stdlib.h> to #include <cstdlib> this made the std namespace "visible" to Eclipse and removed the error.
This worked for me on Eclipse IDE for C/C++ Developers Version: 2020-03 (4.15.0) Build id: 20200313-1211. Also, my code is cross-compiled.
Create a new project making sure it's created as a cross-compiled solution. You have to add the /usr/bin directory that matches your cross-compiler location.
Add the C and C++ headers for the cross-compiler in the Project Properties.
For C: Project > Properties > C/C++ General > Paths and Symbols > Includes > GNU C. Add... -> The path to your /usr/include directory from your cross-compiler.
For C++: Project > Properties > C/C++ General > Paths and Symbols > Includes > GNU C++. Add... -> The path to your /usr/include/c++/ directory from your cross-compiler.
If you don't know your gcc version, type this in a console (make sure it's your cross gcc binary):
gcc -v
Modify the dialect for the cross-compilers (this was the trick).
For C: Project > Properties > C/C++ Build > Settings > Tool Settings > Cross GCC Compiler > Dialect. Set to ISO C99 (-std=C99) or whatever fits your C files standard.
For C++: Project > Properties > C/C++ Build > Settings > Tool Settings > Cross G++ Compiler > Dialect. Set to ISO C++14 (-std=c++14) or whatever fits your C++ files standard.
If needed, re-index all your project by right-clicking the project > Index > Rebuild.
The problem you are reporting seems to me caused by the following:
you are trying to compile C code and the source file has .cpp extension
you are trying to compile C++ code and the source file has .c extension
In such situation Eclipse cannot recognize the proper compiler to use.
Try restart Eclipse first, in my case I change different Compiler setting of the project then it shows this message, after restart it works.