[LLVMdev] Jumping to a fixed address in Clang (original) (raw)

David Meyer pdox at google.com
Fri Sep 16 17:37:40 PDT 2011


I am compiling some code with Clang which needs to jump to a fixed address to perform a "syscall". These fixed addresses contain valid code.

I noticed that this code produces a warning:

typedef void (*exit_syscall_type) (int status) attribute((noreturn)); void _exit(int status) attribute ((noreturn)); void _exit(int status) { ((exit_syscall_type)0x10000)(status); }

This (seemingly equivalent) code does not:

typedef void (*exit_syscall_type) (int status) attribute((noreturn)); void _exit(int status) attribute ((noreturn)); void _exit(int status) { exit_syscall_type ptr = (exit_syscall_type)0x10000; ptr(status); }

The warning produced is:

warning: function declared 'noreturn' should not return [-Winvalid-noreturn]

Is this discrepancy intentional?



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