The TCB_GET32() and TCB_GET64() macros in the i386 and amd64-specific
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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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=228536
@ -71,7 +71,7 @@ struct tcb {
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u_long __i; \
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u_long __i; \
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__asm __volatile("movq %%fs:%1, %0" \
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__asm __volatile("movq %%fs:%1, %0" \
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: "=r" (__i) \
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: "=r" (__i) \
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: "m" (*(u_long *)(__tcb_offset(name)))); \
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: "m" (*(volatile u_long *)(__tcb_offset(name)))); \
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__result = (__tcb_type(name))__i; \
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__result = (__tcb_type(name))__i; \
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\
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\
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__result; \
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__result; \
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@ -70,7 +70,7 @@ struct tcb {
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u_int __i; \
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u_int __i; \
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__asm __volatile("movl %%gs:%1, %0" \
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__asm __volatile("movl %%gs:%1, %0" \
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: "=r" (__i) \
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: "=r" (__i) \
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: "m" (*(u_int *)(__tcb_offset(name)))); \
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: "m" (*(volatile u_int *)(__tcb_offset(name)))); \
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__result = (__tcb_type(name))__i; \
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__result = (__tcb_type(name))__i; \
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\
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\
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__result; \
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__result; \
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