On 2014-11-25 22:53, Michal Marek wrote: > Dne 6.11.2014 v 01:58 Ben Hutchings napsal(a): >> gcc 4.8 and later include <stdc-predef.h> by default. In some >> versions of eglibc that includes <bits/predefs.h>, but that may be >> missing when building with a biarch compiler. Also <stdc-predef.h> >> itself could be missing as we are only trying to build a kernel, not >> userland. >> >> The -nostdinc option disables this, though it isn't explicitly >> documented. This option is already used when actually building >> the kernel, but not by cc-option and other tests. This can result >> in silently miscompiling the kernel. >> >> References: https://bugs.debian.org/717557 >> References: https://bugs.debian.org/726861 >> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> >> --- >> This specific issue appeared and then was fixed in Debian about a year >> ago, but it seems like it can also affect cross-builds. >> >> It may also be worth adding some sort of sanity test, so we stop >> immediately if $(cc-option $(empty),broken) yields 'broken'. >> >> Ben. >> >> Makefile | 4 +++- >> scripts/Kbuild.include | 15 ++++++++------- >> 2 files changed, 11 insertions(+), 8 deletions(-) >> >> diff --git a/Makefile b/Makefile >> index ffc1ce2..c0fbf67 100644 >> --- a/Makefile >> +++ b/Makefile >> @@ -619,6 +619,8 @@ endif >> # Tell gcc to never replace conditional load with a non-conditional one >> KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) >> >> +NOSTDINC_FLAGS += -nostdinc >> + >> ifdef CONFIG_READABLE_ASM >> # Disable optimizations that make assembler listings hard to read. >> # reorder blocks reorders the control in the function >> @@ -742,7 +744,7 @@ KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once) >> endif >> >> # arch Makefile may override CC so keep this after arch Makefile is included >> -NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) >> +NOSTDINC_FLAGS += -isystem $(shell $(CC) -print-file-name=include) > > Why not simply move the whole assignment up? Ah, I see the reason now -- we need $(CC) for the second part of the assignment. > Also, there are two > cc-option tests and one cc-disable-warning test before the first part > assignment. Looks like a result of a mismerge. But this still looks like a bug to me. Michal -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
