curcpu false positive?
Hello, I'm looking at some Clang Static Analyzer reports in the kernel, and a lot of them point back to a null pointer dereference in __pcpu_type (sys/amd64/include/pcpu.h:102) which is defined as: 102 /* 103 * Evaluates to the type of the per-cpu variable name. 104 */ 105 #define __pcpu_type(name) \ 106 __typeof(((struct pcpu *)0)-name) Which indeed looks like a NULL pointer dereference. Looking at the latest commit message there, I'm sure the code is correct, but I'm unsure why the null pointer is OK. I'd appreciate an explanation :-) Thanks, Erik ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to freebsd-hackers-unsubscr...@freebsd.org
Re: curcpu false positive?
on 11/10/2012 16:06 Erik Cederstrand said the following: Hello, I'm looking at some Clang Static Analyzer reports in the kernel, and a lot of them point back to a null pointer dereference in __pcpu_type (sys/amd64/include/pcpu.h:102) which is defined as: 102/* 103* Evaluates to the type of the per-cpu variable name. 104*/ 105 #define __pcpu_type(name) \ 106 __typeof(((struct pcpu *)0)-name) Which indeed looks like a NULL pointer dereference. Looking at the latest commit message there, I'm sure the code is correct, but I'm unsure why the null pointer is OK. I'd appreciate an explanation :-) Read about __typeof [1]. It's evaluated at compile time, so actual value of an expression does not matter at all. [1] http://gcc.gnu.org/onlinedocs/gcc/Typeof.html -- Andriy Gapon ___ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to freebsd-hackers-unsubscr...@freebsd.org
