Trivial C++ code passes in a test project and fails in the main one - c++

Question

These two trivial lines of code:
const bool equal = (HUGE_VALF == HUGE_VALF);
static_assert(equal == true, "Fatal error");
in a test program work perfectly (no warnings and no errors).
When I copy them in the main project, I get this error on the assert:
error C2057: expected constant expression
Here the equal object is a constant with value = true.
Those lines of code are in both cases inside functions.
The two projects have identical settings (C++11, Visual C++ 2013 compiler, Visual C++ 2019 IDE, /W4, no optimizations).
What could be the reason of this different behaviour from the compiler?

Answer 1

When a newer Visual Studio IDE (like VS 2019) loads an older project for the first time, it asks to retarget the project. If You have the old Visual Studio installed, You can reject this action. Then the compiler from the original VS will be used by the newer IDE.
After loading the solution, in the Solution Explorer next to the project name, You will have the Visual Studio which will be used to compile the project.
If the paranthesis is missing, that means the compiler and standard library from the current Visual Studio is been used.
As mentioned in the comments:
I have no parenthesis after the project name (if I am looking in the right place). However, I realised about the issue in the include file paths: Test Project: 14.24.28314\include\cmath; Main Project: Microsoft Visual Studio 12.0\VC\include\cmath, i.e. a much older version, that internally still relies on the C math.h header. So, same compiler (VS2013), different libraries...
This indicates that You have most probably retargeted the project or created a new project in VS 2019.
To make a project in VS 2019 make use of the older compiler, You need to got to the project Properties -> Configuration Properties -> General -> Platform Toolset and change it to the appropriate Visual Studio.
Also make sure that all configurations (Debug, Release,...) for all machine types (32bit, 64 bit) have this setting the same value.
Because the test project is using VS 2019 - it has all the required definitions - so it works.
So the issue is that most probably, VS 2013 standard library is not C++11 complete and does NOT have a definition for HUGE_VALF.
But it could contain a definition for HUGE_VAL