+ revert-kbuild-fix-wimplicit-function-declaration-in-license_is_gpl_compatible.patch added to mm-hotfixes-unstable branch

+ revert-kbuild-fix-wimplicit-function-declaration-in-license_is_gpl_compatible.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: revert "kbuild: fix -Wimplicit-function-declaration in license_is_gpl_compatible"
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     revert-kbuild-fix-wimplicit-function-declaration-in-license_is_gpl_compatible.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/revert-kbuild-fix-wimplicit-function-declaration-in-license_is_gpl_compatible.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Andrew Morton <akpm@linux-foundation.org>
Subject: revert "kbuild: fix -Wimplicit-function-declaration in license_is_gpl_compatible"
Date: Mon Nov 28 01:21:40 PM PST 2022

It causes build failures with unusual CC/HOSTCC combinations.

Quoting
https://lkml.kernel.org/r/A222B1E6-69B8-4085-AD1B-27BDB72CA971@goldelico.com:

  HOSTCC  scripts/mod/modpost.o - due to target missing
In file included from include/linux/string.h:5,
                 from scripts/mod/../../include/linux/license.h:5,
                 from scripts/mod/modpost.c:24:
include/linux/compiler.h:246:10: fatal error: asm/rwonce.h: No such file or directory
  246 | #include <asm/rwonce.h>
      |          ^~~~~~~~~~~~~~
compilation terminated.

...

The problem is that HOSTCC is not necessarily the same compiler or even
architecture as CC and pulling in <linux/compiler.h> or <asm/rwonce.h>
files indirectly isn't a good idea then.

My toolchain is providing HOSTCC = gcc (MacPorts) and CC = arm-linux-gnueabihf
(built from gcc source) and all running on Darwin.

If I change the include to <string.h> I can then "HOSTCC scripts/mod/modpost.c"
but then it fails for "CC kernel/module/main.c" not finding <string.h>:

  CC      kernel/module/main.o - due to target missing
In file included from kernel/module/main.c:43:0:
./include/linux/license.h:5:20: fatal error: string.h: No such file or directory
 #include <string.h>
                    ^
compilation terminated.

Reportd-by: "H. Nikolaus Schaller" <hns@goldelico.com>
Cc: Sam James <sam@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/license.h |    2 --
 1 file changed, 2 deletions(-)

--- a/include/linux/license.h~revert-kbuild-fix-wimplicit-function-declaration-in-license_is_gpl_compatible
+++ a/include/linux/license.h
@@ -2,8 +2,6 @@
 #ifndef __LICENSE_H
 #define __LICENSE_H
 
-#include <linux/string.h>
-
 static inline int license_is_gpl_compatible(const char *license)
 {
 	return (strcmp(license, "GPL") == 0
_

Patches currently in -mm which might be from akpm@linux-foundation.org are

mm-replace-vm_warn_on-to-pr_warn-if-the-node-is-offline-with-__gfp_thisnode-v4-fix.patch
mm-replace-vm_warn_on-to-pr_warn-if-the-node-is-offline-with-__gfp_thisnode-v4-fix-2.patch
revert-kbuild-fix-wimplicit-function-declaration-in-license_is_gpl_compatible.patch
mm-memremap_pages-replace-zone_device_page_init-with-pgmap_request_folios-fix.patch
mm-gup-remove-foll_migration-fix.patch
mm-memremap-introduce-pgmap_request_folio-using-pgmap-offsets-fix.patch
mm-memremap-introduce-pgmap_request_folio-using-pgmap-offsets-fix-2.patch
kasan-allow-sampling-page_alloc-allocations-for-hw_tags-fix.patch
mm-hugetlb-convert-move_hugetlb_state-to-folios-fix.patch
mm-introduce-encoded-page-pointers-with-embedded-extra-bits-fix.patch
mm-delay-page_remove_rmap-until-after-the-tlb-has-been-flushed-fix.patch
mm-document-sys-class-bdi-bdi-min_bytes-knob-fix.patch
mm-document-sys-class-bdi-bdi-max_ratio_fine-knob-fix.patch
mm-document-sys-class-bdi-bdi-min_ratio_fine-knob-fix.patch