Currently the encoding of documents generated by DocBook depends on
the current locale.  Make the output reproducible independently of
the locale, by setting the encoding to UTF-8 (LC_CTYPE=C.UTF-8) by
preference, or ASCII (LC_CTYPE=C) as a fallback.

LC_CTYPE can normally be overridden by LC_ALL, but the top-level
Makefile unsets that.

Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
v2: Rebase on 4.3-rc3.
    Add an explanatory comment to check-lc_type.c.

 Documentation/DocBook/Makefile |  6 ++++++
 Makefile                       |  2 +-
 scripts/Makefile               |  7 +++++--
 scripts/check-lc_ctype.c       | 11 +++++++++++
 4 files changed, 23 insertions(+), 3 deletions(-)
 create mode 100644 scripts/check-lc_ctype.c

diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile
index 93eff64..d254496 100644
--- a/Documentation/DocBook/Makefile
+++ b/Documentation/DocBook/Makefile
@@ -69,6 +69,12 @@ installmandocs: mandocs
 KERNELDOCXMLREF = $(srctree)/scripts/kernel-doc-xml-ref
 KERNELDOC       = $(srctree)/scripts/kernel-doc
 DOCPROC         = $(objtree)/scripts/docproc
+CHECK_LC_CTYPE = $(objtree)/scripts/check-lc_ctype
+
+# Use a fixed encoding - UTF-8 if the C library has support built-in
+# or ASCII if not
+LC_CTYPE := $(call try-run, LC_CTYPE=C.UTF-8 $(CHECK_LC_CTYPE),C.UTF-8,C)
+export LC_CTYPE
 
 XMLTOFLAGS = -m $(srctree)/$(src)/stylesheet.xsl
 XMLTOFLAGS += --skip-validation
diff --git a/Makefile b/Makefile
index 84f4b31..d23d2e9 100644
--- a/Makefile
+++ b/Makefile
@@ -1336,7 +1336,7 @@ $(help-board-dirs): help-%:
 # Documentation targets
 # ---------------------------------------------------------------------------
 %docs: scripts_basic FORCE
-       $(Q)$(MAKE) $(build)=scripts build_docproc
+       $(Q)$(MAKE) $(build)=scripts build_docproc build_check-lc_ctype
        $(Q)$(MAKE) $(build)=Documentation/DocBook $@
 
 else # KBUILD_EXTMOD
diff --git a/scripts/Makefile b/scripts/Makefile
index 1b26617..fd0d53d 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -7,6 +7,7 @@
 # conmakehash:   Create chartable
 # conmakehash:  Create arrays for initializing the kernel console tables
 # docproc:       Used in Documentation/DocBook
+# check-lc_ctype: Used in Documentation/DocBook
 
 HOST_EXTRACFLAGS += -I$(srctree)/tools/include
 
@@ -27,14 +28,16 @@ HOSTLOADLIBES_extract-cert = -lcrypto
 always         := $(hostprogs-y) $(hostprogs-m)
 
 # The following hostprogs-y programs are only build on demand
-hostprogs-y += unifdef docproc
+hostprogs-y += unifdef docproc check-lc_ctype
 
 # These targets are used internally to avoid "is up to date" messages
-PHONY += build_unifdef build_docproc
+PHONY += build_unifdef build_docproc build_check-lc_ctype
 build_unifdef: $(obj)/unifdef
        @:
 build_docproc: $(obj)/docproc
        @:
+build_check-lc_ctype: $(obj)/check-lc_ctype
+       @:
 
 subdir-$(CONFIG_MODVERSIONS) += genksyms
 subdir-y                     += mod
diff --git a/scripts/check-lc_ctype.c b/scripts/check-lc_ctype.c
new file mode 100644
index 0000000..9097ff5
--- /dev/null
+++ b/scripts/check-lc_ctype.c
@@ -0,0 +1,11 @@
+/*
+ * Check that a specified locale works as LC_CTYPE.  Used by the
+ * DocBook build system to probe for C.UTF-8 support.
+ */
+
+#include <locale.h>
+
+int main(void)
+{
+       return !setlocale(LC_CTYPE, "");
+}
-- 
Ben Hutchings
All extremists should be taken out and shot.

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