The Intel C++ compiler documentation gives a large range of GCC versions in the system requirements, eg. for Intel 18.0 it says that:
gcc versions 4.3 - 6.3 supported
(remember prior to version 5 GCC only updated the minor version number for each major release).
However, this is not the full story, if one reads the Intel C++ Compiler 18.0 Developer Guide and Reference, specifically the subsection 'How the Intel Compiler Uses GCC' under 'GCC* Compatibility and Interoperability' section then it makes clear the Intel compiler will behave like the underlying GCC version with respect to available features and behaviour. This means if you want C++14 standard you must use a GCC with this available, i.e. GCC 5 or greater. Taking this into account, the base GCC you need for Intel 18.0 C++ compiler with C++14 features is version 5 or 6. Any higher and Intel does not support this GCC with it's compiler (I tried myself and saw a range of problems), lower than this and you don't have a C++14 standard compiler.
gcc versions 4.3 - 6.3 supported
(remember prior to version 5 GCC only updated the minor version number for each major release).
However, this is not the full story, if one reads the Intel C++ Compiler 18.0 Developer Guide and Reference, specifically the subsection 'How the Intel Compiler Uses GCC' under 'GCC* Compatibility and Interoperability' section then it makes clear the Intel compiler will behave like the underlying GCC version with respect to available features and behaviour. This means if you want C++14 standard you must use a GCC with this available, i.e. GCC 5 or greater. Taking this into account, the base GCC you need for Intel 18.0 C++ compiler with C++14 features is version 5 or 6. Any higher and Intel does not support this GCC with it's compiler (I tried myself and saw a range of problems), lower than this and you don't have a C++14 standard compiler.
Intel 2019
For Intel 2019 the range of GCC supported is 4.3 - 8.x. This means for C++14 support the possible GCC versions are 5 - 8.
