C Error nullptr was not declared in this scope in Eclipse IDE

Question

I am running Eclipse Helios and I have g  -4 6 installed  Hope I am not wrong that g  4 6 implements C   11 features  I have created a C   project which uses the nullptr and auto keywords  The build gives the following errors -      filename  cpp 13 13  error     nullptr    was not declared in this scope      filename  cpp 14 2  warning     auto    will change meaning in C  0x  please remove it  -Wc  0x-compat    Actually it was building fine until yesterday  I am getting these from nowhere today  Please help me solve this problem

User · Answer

Is that an actual compiler error or a Code Analysis error? Some times the code analysis can be a bit sketchy and report non-valid errors.

To turn off code analysis for the project, right click on your project in the Project Explorer, click on Properties, then go to the C/C++ General tab, then Code Analysis. Then click on "Use Project Settings" and disable the ones that you do not wish for.

Also, are you sure you are compiling with the C++11 compiler?

User · Answer

According to the GCC page for C  11   To enable C  0x support  add the command-line parameter -std c  0x to your g   command line  Or  to enable GNU extensions in addition to C  0x extensions  add -std gnu  0x to your g   command line  GCC 4 7 and later support -std c  11 and -std gnu  11 as well   Did you compile with -std gnu  0x

User · Answer

You are using g   4 6 version you must invoke the flag -std c  0x to compile     g   -std c  0x   cpp -o output

User · Answer

I add the   -std c  0x  after  -c -fmessage-length 0  under Project Properties -  C C   Build -  Settings -  GCC C   Compiler -  Miscellaneous  Dont t forget to add the comma     as the seperator

User · Answer

Go to Settings -  Compiler    And add flag to  Have g   follow the coming C  0x ISO C   language standard  std c  0x

User · Answer

Finally found out what to do  Added the -std c  0x compiler argument under Project Properties -  C C   Build -  Settings -  GCC C   Compiler -  Miscellaneous  It works now   But how to add this flag by default for all C   projects  Anybody

User · Answer

Trying with a different version of gcc worked for me - gcc 4 9 in my case

[c++] C++ Error 'nullptr was not declared in this scope' in Eclipse IDE

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