I am using MDK-ARM V5.37 with arm compile V5 and have noticed that _MSC_VER is defined until I perform a build at which point it becomes undefined.
I have no idea where/why it is defined, it certainly isn't in my code. I don't understand why it is defined and then becomes undefined at the point I perform a build.
It can easily be demonstrated in "main.c" as follows:
#if defined(_MSC_VER) && _MSC_VER >= 1700 int a = 1; #endif int main(void) { int b = a; /* Infinite loop */ while (1) { } }
The Dynamic Syntax Checker is happy with the code and "int a = 1;" is not greyed out, implying _MSC_VER is defined.
Now compile the code and it gives error in main() stating that "a" is undefined.
This only happens when configured for arm compiler V5. When configured for arm compiler V6 "int a = 1;" is greyed out and _MSC_VER is not defined before/during build.
Nothing like that I'm afraid. There is no doubt that _MSC_VER is defined until the build is started. Try it yourself and you will see.
Actually, no. There is in fact all kind of doubt, mostly because the phrase "until the build is started" makes no sense.
What most likely happens is that for some silly reason this macro (which is supposed to identify the Microsoft C compiler for Windows) is believed to be defined by the Syntax checker engine, but it is (quite correctly) not defined for the compiler. Those are two separate tools, not two different points in time, which is why the qualifier "until" makes no sense here.
I'm merely stating the way it behaves - you're being pedantic. I will rephrase - it BEHAVES as if it is defined but when the build starts it is clearly not defined as code within the #if is not compiled. This behaviour is only seen when project configured for V5 compiler, not V6. It may well be a problem with the DSC as it is likely to be influenced by the compiler version.