> On Jul 21, 2016, at 4:00 AM, Ard Biesheuvel <[email protected]> wrote: > > On 20 July 2016 at 23:09, Andrew Fish <[email protected]> wrote: >> It looks like clang has added a warning to detect infinite recursion and I'm >> seeing the failure here: >> >> https://github.com/tianocore/edk2/blob/master/StdLib/LibC/StdLib/Environs.c#L123 >> void >> _Exit(int status) >> { >> gMD->ExitValue = status; // Save our exit status. Allows a status >> of 0. >> longjmp(gMD->MainExit, 0x55); // Get out of here. longjmp can't return >> 0. Use 0x55 for a non-zero value. >> >> #ifdef __GNUC__ >> _Exit(status); /* Keep GCC happy - never reached */ >> #endif >> } >> >> This is the compiler warning. >> >> error: all paths through this function will call itself >> [-Werror,-Winfinite-recursion] >> >> I fixed by replacing the infinite recursion with UNREACHABLE() but I'm not >> sure what the rules are changing this chunk of code? >> > > UNREACHABLE() resolves to an empty string on GCC44 [or it will as soon > as my patch that fixes that is merged, since 4.4 does not implement > __builtin_unreachable()] > > The correct thing would be to set __attribute__((noreturn)) on the > longjmp() prototype [if __GNUC__], but it would be interesting to > understand what GCC was unhappy about to begin with. >
Ard, It looks like _Exit() is __noreturn and longjmp() is not. If I remove the UNREACHABLE() then clang warns: error: function declared 'noreturn' should not return [-Werror,-Winvalid-noreturn] I noticed that a while (1); also fixes the issue. I wonder if UNREACHABLE() should map to while(1) if __builtin_unreachable() does not exist. I'm not sure longjmp() is noreturn as it is really a non local goto. Maybe it is a legacy issue as marking it as noreturn could break existing code (You could start getting unreachable code warnings)? Thanks, Andrew Fish > -- > Ard. > _______________________________________________ > edk2-devel mailing list > [email protected] > https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.01.org_mailman_listinfo_edk2-2Ddevel&d=CwICAg&c=Hw-EJUFt2_D9PK5csBJ29kRV40HqSDXWTLPyZ6W8u84&r=4sdzHKz0eU1vXqaUySVmyA&m=3-VAa-nWtHZ4V-IQPablzh3GOt1QSWpVuCtb1t8t0io&s=53CJFOut17i8QI3_i894rC3YtBXolOZwcqRZ-3bwkdg&e= _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
