versions of pthread_md.h have a special case of dereferencing a null pointer. Clang warns about this with: In file included from lib/libthr/arch/i386/i386/pthread_md.c:36: lib/libthr/arch/i386/include/pthread_md.h:96:10: error: indirection of non-volatile null pointer will be deleted, not trap [-Werror,-Wnull-dereference] return (TCB_GET32(tcb_self)); ^~~~~~~~~~~~~~~~~~~ lib/libthr/arch/i386/include/pthread_md.h:73:13: note: expanded from: : "m" (*(u_int *)(__tcb_offset(name)))); \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ lib/libthr/arch/i386/include/pthread_md.h:96:10: note: consider using __builtin_trap() or qualifying pointer with 'volatile' Since this indirection is done relative to the fs or gs segment, to retrieve thread-specific data, it is an exception to the rule. Therefore, add a volatile qualifier to tell the compiler we really want to dereference a zero address. MFC after: 1 week |
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