package/musl-compat-headers: provide compatibility headers not in musl

musl provides neither sys/queue.h nor sys/cdefs.h. Those two headers are
however quite widely used in a lot of packages (though they should at
least not use cdefs.h which is only full of mostly-legacy macros, and
which is mostly an internal header of glibc and was never really meant to
be exposed to, and used by packages).

But we don't live in an ideal world, so a lot of packages break when
those two headers are missing.

We already took care of sys/queue.h with the netbsd-queue package. But
the need for cdefs.h is getting more and more pressing.

We rename the netbsd-queue package into musl-compat-headers, and we
make it install sys/queue.h (from NetBSD) and sys/cdefs.h (a minimalist
one we bundle in Buildroot). We can't use the cdefs.h from NetBSD
because it includes machine-dependent headers; instead we bundle a very
minimalistic one, that covers only what we need.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Baruch Siach <baruch@tkos.co.il>
Cc: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/Config.in

@@ -1324,7 +1324,7 @@ endif
 	source "package/mpfr/Config.in"
 	source "package/msgpack/Config.in"
 	source "package/mtdev2tuio/Config.in"
-	source "package/netbsd-queue/Config.in"
+	source "package/musl-compat-headers/Config.in"
 	source "package/openblas/Config.in"
 	source "package/orc/Config.in"
 	source "package/p11-kit/Config.in"

package/musl-compat-headers/Config.in

@@ -0,0 +1,2 @@
+config BR2_PACKAGE_MUSL_COMPAT_HEADERS
+	bool

package/musl-compat-headers/cdefs.h

@@ -0,0 +1,51 @@
+/* Copyright (C) 2016 Yann E. MORIN <yann.morin.1998@free.fr>
+ *
+ * This file is in the Public Domain.
+ *
+ * For jurisdictions in which the Public Domain does not exist
+ * or it is not otherwise applicable, this file is licensed CC0
+ * (Creative Commons Zero).
+ */
+
+/* This file contains definitions for non-standard macros defined by
+ * glibc, but quite commonly used in packages.
+ *
+ * Because they are non-standard, musl does not define those macros.
+ * It does not provide cdefs.h either.
+ *
+ * This file is a compatibility header written from scratch, to be
+ * installed when the C library is musl.
+ *
+ * Not all macros from the glibc's cdefs.h are available, only the
+ * most commonly used ones.
+ *
+ * Please refer to the glibc documentation and source code for
+ * explanations about those macros.
+ */
+
+#ifndef BUILDROOT_SYS_CDEFS_H
+#define BUILDROOT_SYS_CDEFS_H
+
+/* Function prototypes. */
+#undef __P
+#define __P(arg) arg
+
+/* C declarations in C++ mode. */
+#ifdef __cplusplus
+# define __BEGIN_DECLS extern "C" {
+# define __END_DECLS   }
+#else
+# define __BEGIN_DECLS
+# define __END_DECLS
+#endif
+
+/* Don't throw exceptions in C functions. */
+#ifndef __cplusplus
+# define __THROW  __attribute__ ((__nothrow__))
+# define __NTH(f) __attribute__ ((__nothrow__)) f
+#else
+# define __THROW
+# define __NTH(f) f
+#endif
+
+#endif /* ifndef BUILDROOT_SYS_CDEFS_H */

package/musl-compat-headers/musl-compat-headers.mk

@@ -0,0 +1,34 @@
+################################################################################
+#
+# musl-compat-headers
+#
+################################################################################
+
+# No main site, just using extra downloads
+MUSL_COMPAT_HEADERS_QUEUE_H = http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/sys/queue.h?rev=1.70
+
+MUSL_COMPAT_HEADERS_EXTRA_DOWNLOADS = $(MUSL_COMPAT_HEADERS_QUEUE_H)
+
+MUSL_COMPAT_HEADERS_LICENSE = BSD-3c, Public Domain or CC0
+MUSL_COMPAT_HEADERS_LICENSE_FILES = queue.h cdefs.h
+
+MUSL_COMPAT_HEADERS_ADD_TOOLCHAIN_DEPENDENCY = NO
+
+# Only installs headers
+MUSL_COMPAT_HEADERS_INSTALL_TARGET = NO
+MUSL_COMPAT_HEADERS_INSTALL_STAGING = YES
+
+# Copying both headers so legal-info finds them (they are _LICENSE_FILES)
+define MUSL_COMPAT_HEADERS_EXTRACT_CMDS
+	$(INSTALL) -m 0644 -D $(DL_DIR)/$(notdir $(MUSL_COMPAT_HEADERS_QUEUE_H)) $(@D)/queue.h
+	$(INSTALL) -m 0644 -D $(MUSL_COMPAT_HEADERS_PKGDIR)/cdefs.h $(@D)/cdefs.h
+endef
+
+define MUSL_COMPAT_HEADERS_INSTALL_STAGING_CMDS
+	$(INSTALL) -D -m 0644 $(@D)/queue.h \
+		$(STAGING_DIR)/usr/include/sys/queue.h
+	$(INSTALL) -D -m 0644 $(@D)/cdefs.h \
+		$(STAGING_DIR)/usr/include/sys/cdefs.h
+endef
+
+$(eval $(generic-package))

package/musl/Config.in

@@ -3,5 +3,6 @@ config BR2_PACKAGE_MUSL
 	depends on BR2_TOOLCHAIN_USES_MUSL
 	default y
 	select BR2_PACKAGE_LINUX_HEADERS
-	select BR2_PACKAGE_NETBSD_QUEUE
 	select BR2_TOOLCHAIN_HAS_SSP
+	# Compatibility headers: cdefs.h, queue.h
+	select BR2_PACKAGE_MUSL_COMPAT_HEADERS

package/musl/musl.mk

@@ -13,10 +13,12 @@ MUSL_LICENSE_FILES = COPYRIGHT
 # cross-compiler and the kernel headers
 MUSL_DEPENDENCIES = host-gcc-initial linux-headers
 
-# musl does not provide a sys/queue.h implementation, so add the
-# netbsd-queue package that will install a sys/queue.h file in the
-# staging directory based on the NetBSD implementation.
-MUSL_DEPENDENCIES += netbsd-queue
+# musl does not provide an implementation for sys/queue.h or sys/cdefs.h.
+# So, add the musl-compat-headers package that will install those files,
+# into the staging directory:
+#   sys/queue.h:  header from NetBSD
+#   sys/cdefs.h:  minimalist header bundled in Buildroot
+MUSL_DEPENDENCIES += musl-compat-headers
 
 # musl is part of the toolchain so disable the toolchain dependency
 MUSL_ADD_TOOLCHAIN_DEPENDENCY = NO

package/netbsd-queue/Config.in

@@ -1,2 +0,0 @@
-config BR2_PACKAGE_NETBSD_QUEUE
-	bool

package/netbsd-queue/netbsd-queue.mk

@@ -1,24 +0,0 @@
-################################################################################
-#
-# netbsd-queue
-#
-################################################################################
-
-NETBSD_QUEUE_VERSION = 1.70
-NETBSD_QUEUE_SITE = http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/sys
-NETBSD_QUEUE_SOURCE = queue.h?rev=$(NETBSD_QUEUE_VERSION)
-NETBSD_QUEUE_LICENSE = BSD-3c
-
-NETBSD_QUEUE_ADD_TOOLCHAIN_DEPENDENCY = NO
-NETBSD_QUEUE_INSTALL_STAGING = YES
-
-define NETBSD_QUEUE_EXTRACT_CMDS
-	cp $(DL_DIR)/$(NETBSD_QUEUE_SOURCE) $(@D)/queue.h
-endef
-
-define NETBSD_QUEUE_INSTALL_STAGING_CMDS
-	$(INSTALL) -D -m 0644 $(@D)/queue.h \
-		$(STAGING_DIR)/usr/include/sys/queue.h
-endef
-
-$(eval $(generic-package))

toolchain/toolchain-external/Config.in

@@ -727,7 +727,8 @@ config BR2_TOOLCHAIN_EXTERNAL_UCLIBC
 config BR2_TOOLCHAIN_EXTERNAL_MUSL
 	bool
 	select BR2_TOOLCHAIN_USES_MUSL
-	select BR2_PACKAGE_NETBSD_QUEUE
+	# Compatibility headers: cdefs.h, queue.h
+	select BR2_PACKAGE_MUSL_COMPAT_HEADERS
 
 if BR2_TOOLCHAIN_EXTERNAL_CUSTOM
 

toolchain/toolchain-external/toolchain-external.mk

@@ -246,11 +246,13 @@ TOOLCHAIN_EXTERNAL_CFLAGS += -msoft-float
 TOOLCHAIN_EXTERNAL_TOOLCHAIN_WRAPPER_ARGS += -DBR_SOFTFLOAT=1
 endif
 
-# musl does not provide a sys/queue.h implementation, so add the
-# netbsd-queue package that will install a sys/queue.h file in the
-# staging directory based on the NetBSD implementation.
+# musl does not provide an implementation for sys/queue.h or sys/cdefs.h.
+# So, add the musl-compat-headers package that will install those files,
+# into the staging directory:
+#   sys/queue.h:  header from NetBSD
+#   sys/cdefs.h:  minimalist header bundled in Buildroot
 ifeq ($(BR2_TOOLCHAIN_USES_MUSL),y)
-TOOLCHAIN_EXTERNAL_DEPENDENCIES += netbsd-queue
+TOOLCHAIN_EXTERNAL_DEPENDENCIES += musl-compat-headers
 endif
 
 # The Linaro toolchain expects the libraries in