Date: Sun, 4 Dec 2005 00:45:18 +0200 From: Ruslan Ermilov <ru@FreeBSD.org> To: current@FreeBSD.org Subject: Beware of subtle bugs due to cpp(1) limitations! Message-ID: <20051203224518.GJ960@ip.net.ua>
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--vbzKE9fGfpHIBC6T Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi there, cpp(1) only supports integer expressions, so the following #define FOO foo #if FOO =3D=3D bar will always evaluate to true, because "foo" and "bar" will be treated as zeroes, as explained in cpp.info. I've only scanned for _MACHINE_ARCH, because that's how I discovered it, and there's a couple of places where the code is broken: sys/dev/isp/isp_freebsd.h:#if _MACHINE_ARCH =3D=3D sparc64 sys/dev/ispfw/ispfw.c:#if _MACHINE_ARCH =3D=3D sparc64 sys/dev/ispfw/ispfw.c:#if _MACHINE_ARCH =3D=3D sparc64 sys/dev/ispfw/ispfw.c:#if _MACHINE_ARCH =3D=3D sparc64 sys/gnu/fs/reiserfs/reiserfs_fs.h:#if (_MACHINE_ARCH =3D=3D amd64) sys/netgraph/ng_vjc.c:#if _MACHINE_ARCH =3D=3D i386 sys/netgraph/ng_vjc.c:#elif _MACHINE_ARCH =3D=3D alpha sys/netgraph/ng_vjc.c:#error Unspported _MACHINE_ARCH In these cases, the right tests would be #ifdef __sparc64__. Other instances (of not _MACHINE_ARCH) may be harder to fix. The ng_vjc.c is a nice example that clearly demonstrates (without compiling the code) that it's broken -- it's compiled on all architectures, but has the following code: #if _MACHINE_ARCH =3D=3D i386 #define NG_VJC_TSTATE_PTR_TYPE &ng_parse_uint32_type #elif _MACHINE_ARCH =3D=3D alpha #define NG_VJC_TSTATE_PTR_TYPE &ng_parse_uint64_type #else #error Unspported _MACHINE_ARCH #endif The season for more bugs of this type is declared open! :-) Cheers, --=20 Ruslan Ermilov ru@FreeBSD.org FreeBSD committer --vbzKE9fGfpHIBC6T Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFDkh/+qRfpzJluFF4RAsuQAJ409WxCpqOhYfOCaOtDp2mKX3a54wCeOj1A lcbvVVME7PjIrinGnefue0A= =suSU -----END PGP SIGNATURE----- --vbzKE9fGfpHIBC6T--
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