Can you please provide a minimal repro?

1. Checkout FreeBSD 11-current sources:

commit 5cfb29320af7efe68fe6aa83e89cc3650167c5f0
Author: ganbold ganbold@FreeBSD.org
Date: Wed May 13 05:46:04 2015 +0000

Delete cpu_do_powersave which is set but never used/tested
serving no useful purpose.

3. Install clang35 from pkg under FreeBSD 9-stable.

4. In /etc/make.conf:

CC=/usr/local/bin/clang35
LD=/usr/local/bin/ld
COMPILER_TYPE=clang
COMPILER_VERSION=30500

5. cd /usr/img/freebsd/sys/modules/sppp
6. bmake -m /usr/img/freebsd/share/mk

Should reproduce.

"Minimal" in this context means a preprocessed .c or .cpp file, without any external dependencies. Also, the exact command line flags used to invoke clang are almost always needed.

Command line:

/usr/local/bin/clang35 -O2 -pipe -fno-strict-aliasing -Werror -D_KERNEL -DKLD_MODULE -nostdinc -fno-common -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float -fno-asynchronous-unwind-tables -ffreestanding -fwrapv -fstack-protector -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual -Wundef -Wno-pointer-sign -fformat-extensions -Wmissing-include-dirs -fdiagnostics-show-option -Wno-unknown-pragmas -Wno-error-tautological-compare -Wno-error-empty-body -Wno-error-parentheses-equality -Wno-error-unused-function -Wno-error-pointer-sign -mno-aes -mno-avx -std=iso9899:1999 -c if_spppsubr.c

See attached if_spppsubr.c

Thank you!

--HPS

Preprocessed file

Right, this is a bug in the FreeBSD-specific -fformat-extensions support, added in the lang/clang35 port. This flag isn't supported by upstream clang, and has been replaced by the format(freebsd_kprintf, x, y) attribute in trunk.

For reference, a minimal example is:

void foo(int, const char *, ...) attribute((format(printf, 2, 3)));

void bar(const unsigned char *p, unsigned short len)
{
foo(-1, " %*D", len, p, "-");
}

Let's move this bug over to the FreeBSD bug tracker:

https://bugs.freebsd.org/200193