What does the fpermissive flag do?
Right from the docs:
-fpermissive
Downgrade some diagnostics about nonconformant code from errors to warnings. Thus, using-fpermissivewill allow some nonconforming code to compile.
Bottom line: don't use it unless you know what you are doing!
When you've written something that isn't allowed by the language standard (and therefore can't really be well-defined behaviour, which is reason enough to not do it) but happens to map to some kind of executable if fed naïvely to the compiling engine, then -fpermissive will do just that instead of stopping with this error message. In some cases, the program will then behave exactly as you originally intended, but you definitely shouldn't rely on it unless you have some very special reason not to use some other solution.
The -fpermissive flag causes the compiler to report some things that are actually errors (but are permitted by some compilers) as warnings, to permit code to compile even if it doesn't conform to the language rules. You really should fix the underlying problem. Post the smallest, compilable code sample that demonstrates the problem.
-fpermissive
Downgrade some diagnostics about nonconformant code from errors to warnings. Thus, using-fpermissivewill allow some nonconforming code to compile.