[clang][Headers] Fix unintentional error in D130800

[ddcc]

Summary

Undefined macros evaluate to zero, so when checking for a smaller value,
we need to include the case when the macro is undefined.

[iana]

That was the only one I saw from D130800, can someone double check me though?

[aaron.ballman]

Undefined macros evaluate to zero, so when checking for a smaller value, we need to include the case when the macro is undefined.

The code being changed already checks defined(__cplusplus) so there no undefined macro value being tested. What's more, if __cplusplus is not defined, we wouldn't even get into this block because we'd have hit line 19 instead. I think the current form is easier to read given the subsequent comment talking about being in C++98 mode (which would be weird to consider for when __cplusplus is not defined), even if the test for defined(__cplusplus) isn't strictly needed.

[ddcc]

I missed line 19, yeah that makes sense. @iana is that ok with you?

[iana]

In D131213#3702699, @ddcc wrote:

I missed line 19, yeah that makes sense. @iana is that ok with you?

Ah, I didn't see that either. Can we just lose the defined on line 26 then? It's redundant and little confusing.

[aaron.ballman]

In D131213#3702707, @iana wrote:

In D131213#3702699, @ddcc wrote:

I missed line 19, yeah that makes sense. @iana is that ok with you?

Ah, I didn't see that either. Can we just lose the defined on line 26 then? It's redundant and little confusing.

I'm fine dropping it (ever so slightly less work for the preprocessor to do in this file), but I don't see what the confusion is with checking whether __cplusplus is defined before testing its value, so I'm also fine with leaving it as-is.

clang/lib/Headers/stdbool.h

  */
 #elif !defined(__cplusplus)
 #define bool _Bool
 #define true 1
 #define false 0
 #elif defined(__GNUC__) && !defined(__STRICT_ANSI__)
 /* Define _Bool as a GNU extension. */
 #define _Bool bool
-#if defined(__cplusplus) && __cplusplus < 201103L
+#if !defined(__cplusplus) || __cplusplus < 201103L
 /* For C++98, define bool, false, true as a GNU extension. */
 #define bool bool
 #define false false
 #define true true
 #endif
 #endif
 
 #endif /* __STDBOOL_H */