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If the intention is to expand the __LINE__ macro, which is likely the case here, the following definition for JOIN() is noncompliant:

#define JOIN(x, y) x ## y

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To get the macro to expand, a second level of indirection is required, as shown by this compliant solution:

#define JOIN(x, y) JOIN_AGAIN(x, y)
#define JOIN_AGAIN(x, y) x ## y

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This example is noncompliant if the programmer's intent is to expand the macro before stringification:

#define str(s) #s
#define foo 4

str(foo)

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To stringify the result of expansion of a macro argument, you must use two levels of macros:

#define xstr(s) str(s)
#define str(s) #s
#define foo 4

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