This diagnostic message lets you find all the 'long' types used in a program.
Of course, presence of the 'long' type in a program is not an error in itself. But you may need to review all the fragments of the program text where this type is used when you create portable 64-bit code that must work well in Windows and Linux.
Windows and Linux use different data models for the 64-bit architecture. A data model means correlations of sizes of base data types such as int, float, pointer, etc. Windows uses the LLP64 data model while Linux uses the LP64 data model. In these models, the sizes of the 'long' type are different.
In Windows (LLP64), the size of the 'long' type is 4 bytes.
In Linux (LP64), the size of the 'long' type is 8 bytes.
The difference of the 'long' type's sizes may make files' formats incompatible or cause errors when developing code executed in Linux and Windows. So if you want, you may use PVS-Studio to review all the code fragments where the 'long' type is used.