xen: Deal with stdarg.h and -nostdinc

For compiling the xen kernel we use -nostdinc which means we don't want to rely on any external headers. That also counts vor stdarg.h.

Use the external header when we compile the tools. Adapt libelf-loader.c which is compiled in the kernel and with the tools.

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diff -r 24b01e02ea17 xen/common/libelf/libelf-loader.c
@@ -16,7 +16,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
-#include <stdarg.h>
+#include "../../include/xen/stdarg.h"
 
 #include "libelf-private.h"
 

diff -r 24b01e02ea17 xen/include/xen/stdarg.h
@@ -1,5 +1,13 @@
-#if defined(__OpenBSD__)
-#  include "/usr/include/stdarg.h"
+#ifndef _XEN_STDARG_H_
+#define _XEN_STDARG_H_
+
+#if defined(__XEN__)
+typedef __builtin_va_list va_list;
+#define va_start(ap, last)    __builtin_stdarg_start((ap), (last))
+#define va_end(ap)            __builtin_va_end(ap)
+#define va_arg                __builtin_va_arg
 #else
 #  include <stdarg.h>
 #endif
+
+#endif	/* _XEN_STDARG_H_ */

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Forgot to mention: Please apply this to xen-4.1-testing, too.

Christoph

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Does the current approach not work for you?

-- Keir

I think using compiler provided headers is fine, and I have to admit I don't like the open-coding of various definitions to gcc builtins - if gcc changes anything here, we'll break (which after all is why the compiler provides this header instead of the platform).

Jan

Christoph Egger writes ("[Xen-devel] [PATCH] xen: Deal with stdarg.h and -nostdinc"):

Right, OK, but:

-#include <stdarg.h>
+#include "../../include/xen/stdarg.h"

Firstly, is this correct for all uses of libelf-loader ? This file is compiled both for use inside Xen and for use on the host. In the latter case it /should/ use the system's stdarg.h.

Also, this kind of relative path should not be necessary. The relevant files should be on the include path.

So I think this should be fixed by arranging that your new stdarg.h is on the relevant include path, not by changing the .c file.

Ian.

Not really. We are only doing the same as Linux right now. I do note that they add an -isystem option to their command line, with a gcc include path that they presumably dump out of gcc in some standard way. However, our current approach seems to work, if it fails to work in some situation it is likely to be pretty obvious (build or link failure), and we can fix it then. This stuff can be moderately fragile, and we've now had no actual bug reports about it in a long while.

-- Keir

The cross-compiling facility in NetBSD has been further improved which made gcc more pendantic for this. -nostdinc is used and -isystem is *not* used.

Here is a full error message:

gcc -O2 -I/usr/include -I/usr/pkg/include -O2 -fomit-frame-pointer -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -O2 -fomit-frame-pointer -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -O2 -fomit-frame-pointer -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -DNDEBUG -nostdinc -fno-builtin -fno-common -Wredundant-decls -iwithprefix include -Werror -Wno-pointer-arith -pipe -I/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include -I/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/asm-x86/mach-generic -I/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/asm-x86/mach-default -msoft-float -fno-stack-protector -fno-exceptions -mno-red-zone
-fpic -fno-asynchronous-unwind-tables -DGCC_HAS_VISIBILITY_ATTRIBUTE
-g -D__XEN__ -MMD -MF .xen.d -O2 -fomit-frame-pointer -m64 -fno-strict-aliasing -std=gnu99 -Wall -Wstrict-prototypes -Wno-unused-value -Wdeclaration-after-statement -DNDEBUG -nostdinc -fno-builtin -fno-common -Wredundant-decls -iwithprefix include -Werror -Wno-pointer-arith -pipe -I/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include -I/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/asm-x86/mach-generic -I/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/asm-x86/mach-default -msoft-float -fno-stack-protector -fno-exceptions -mno-red-zone -fpic -fno-asynchronous-unwind-tables -DGCC_HAS_VISIBILITY_ATTRIBUTE -g -D__XEN__ -MMD -MF .asm-offsets.s.d -S -o asm-offsets.s x86_64/asm-offsets.c In file included from /tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/lib.h:5,
from
/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/asm/system.h:4,
from
/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/spinlock.h:5,
from
/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/sched.h:7,

                 from x86_64/asm-offsets.c:10:

/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/stdarg.h:4:22: error: stdarg.h: No such file or directory In file included from /tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/asm/system.h:4,
from
/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/spinlock.h:5,
from
/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/sched.h:7,

                 from x86_64/asm-offsets.c:10:

/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/lib.h:86: error: expected declaration specifiers or '...' before 'va_list' /tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/lib.h:90: error: expected declaration specifiers or '...' before 'va_list' /tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/lib.h:94: error: expected declaration specifiers or '...' before 'va_list' In file included from /tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/acpi/acpi.h:61,
from
/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/xen/acpi.h:34,
from
/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/acpi/apei.h:8,
from
/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/asm/fixmap.h:23,

                 from x86_64/asm-offsets.c:12:

/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/include/acpi/acpiosxf.h:257: error: expected declaration specifiers or '...' before 'va_list' gmake[3]: *** [asm-offsets.s] Error 1
gmake[3]: Leaving directory `/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/arch/x86'
gmake[2]: *** [/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen/xen] Error 2
gmake[2]: Leaving directory `/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen'
gmake[1]: *** [install] Error 2
gmake[1]: Leaving directory `/tmp/pkgsrc-obj/sysutils/xenkernel41/work.ixp/xen-4.1.0/xen'

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So where does NetBSD get its stdarg.h from in this case? It's somewhat bogus to roll your own, as it contains compiler-specific intrinsics.

-- Keir

-isystem must be *explicitely* specified now.

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Christoph Egger writes ("Re: [Xen-devel] [PATCH] xen: Deal with stdarg.h and -nostdinc"):

Compiling Xen with some kind of native "cross-compiling facility" provided by NetBSD is NOT SUPPORTED.

Please do NOT send any more patches to Xen to try to make it work.

Ian.

This is exactly what happens in conjunction with the other diff. In the first case there is __XEN__ defined and in the latter case __XEN__ is *not* defined.

I tried <xen/stdarg.h> but then compiling the tools failed.

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