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_MSC_VER defined but not during build

G .

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.

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  • 0

    The most likely reason is, that in uVision the compiler to compile the source, Arm Compiler 5, is different to the compiler used for DSC, Arm Compiler 6/clang. The Arm Compiler 6/clang defines the _MSC_VER on Windows and the Arm Compiler 5 does not know it. There are other situations when the DSC might report errors on Arm Compiler 5 specific syntax, like embedded assembler usage.

    Not sure what your code should actually achieve. There are already discussions out there, like this on Stack Overflow, also mentioning how to check for specific compilers, if this is what you want to do.

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  • 0

    The most likely reason is, that in uVision the compiler to compile the source, Arm Compiler 5, is different to the compiler used for DSC, Arm Compiler 6/clang. The Arm Compiler 6/clang defines the _MSC_VER on Windows and the Arm Compiler 5 does not know it. There are other situations when the DSC might report errors on Arm Compiler 5 specific syntax, like embedded assembler usage.

    Not sure what your code should actually achieve. There are already discussions out there, like this on Stack Overflow, also mentioning how to check for specific compilers, if this is what you want to do.

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