default features: make musl usable without feature test macros

the old behavior of exposing nothing except plain ISO C can be
obtained by defining __STRICT_ANSI__ or using a compiler option (such
as -std=c99) that predefines it. the new default featureset is POSIX
with XSI plus _BSD_SOURCE. any explicit feature test macros will
inhibit the default.

installation docs have also been updated to reflect this change.

INSTALL

@@ -76,14 +76,9 @@ musl-gcc hello.c
 ./a.out
 
 To configure autoconf-based program to compile and link against musl,
-you may wish to use:
+set the CC variable to musl-gcc when running configure, as in:
 
-CC="musl-gcc -D_GNU_SOURCE" ./configure ...
-
-Correctly-written build systems should not need -D_GNU_SOURCE as part
-of $CC, but many programs do not use feature-test macros correctly and
-simply assume the compiler will automatically give them the kitchen
-sink, so the above command is an easy workaround.
+CC=musl-gcc ./configure ...
 
 You will probably also want to use --prefix when building libraries to
 ensure that they are installed under the musl prefix and not in the
@@ -140,9 +135,3 @@ dynamic linker (program interpreter) is /lib/ld-musl-$ARCH.so.1. If
 you're using static linking only, you might instead check the symbols
 and look for anything suspicious that would indicate your old glibc or
 uClibc was used.
-
-When building programs against musl, you may still want to ensure the
-appropriate feature test macros get defined, as in:
-
-CC="gcc -D_GNU_SOURCE" ./configure ...
-

include/aio.h

@@ -5,12 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
-
+#include <features.h>
 #include <signal.h>
 #include <time.h>
 

include/assert.h

@@ -1,11 +1,6 @@
-#undef assert
+#include <features.h>
 
-#if __STDC_VERSION__ >= 201112L
-#elif defined(__GNUC__)
-#define _Noreturn __attribute__((__noreturn__))
-#else
-#define _Noreturn
-#endif
+#undef assert
 
 #ifdef NDEBUG
 #define	assert(x) (void)0

include/ctype.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 int   isalnum(int);
 int   isalpha(int);
 int   isblank(int);

include/dirent.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define __NEED_ino_t
 #define __NEED_off_t

include/dlfcn.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define RTLD_LAZY   1
 #define RTLD_NOW    2

include/endian.h

@@ -1,9 +1,7 @@
 #ifndef _ENDIAN_H
 #define _ENDIAN_H
 
-#if __STDC_VERSION__ >= 199901L || defined(__cplusplus)
-#define __inline inline
-#endif
+#include <features.h>
 
 #define __LITTLE_ENDIAN 1234
 #define __BIG_ENDIAN 4321

include/fcntl.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_off_t
 #define __NEED_pid_t
 #define __NEED_mode_t

include/features.h

@@ -1 +1,28 @@
-#warning "features.h is bogus"
+#ifndef _FEATURES_H
+#define _FEATURES_H
+
+#if !defined(_POSIX_SOURCE) && !defined(_POSIX_C_SOURCE) \
+ && !defined(_XOPEN_SOURCE) && !defined(_GNU_SOURCE) \
+ && !defined(_BSD_SOURCE) && !defined(__STRICT_ANSI__)
+#define _BSD_SOURCE 1
+#define _XOPEN_SOURCE 700
+#endif
+
+#if __STDC_VERSION__ >= 199901L
+#define __restrict restrict
+#elif !defined(__GNUC__)
+#define __restrict
+#endif
+
+#if __STDC_VERSION__ >= 199901L || defined(__cplusplus)
+#define __inline inline
+#endif
+
+#if __STDC_VERSION__ >= 201112L
+#elif defined(__GNUC__)
+#define _Noreturn __attribute__((__noreturn__))
+#else
+#define _Noreturn
+#endif
+
+#endif

include/fnmatch.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define	FNM_PATHNAME 0x1
 #define	FNM_NOESCAPE 0x2
 #define	FNM_PERIOD   0x4

include/ftw.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 /* Normally we do not nest header includes. However useless bloat
  * like ftw may be treated as a special case. Otherwise we would
  * have to deal with duplicating all the stat.h mess. */

include/glob.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define __NEED_size_t
 

include/grp.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_size_t
 #define __NEED_gid_t
 

include/limits.h

@@ -1,6 +1,8 @@
 #ifndef _LIMITS_H
 #define _LIMITS_H
 
+#include <features.h>
+
 /* Most limits are system-specific */
 
 #include <bits/limits.h>

include/locale.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #undef NULL
 #ifdef __cplusplus
 #define NULL 0

include/math.h

@@ -5,9 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L || defined(__cplusplus)
-#define __inline inline
-#endif
+#include <features.h>
 
 #define __NEED_float_t
 #define __NEED_double_t

include/net/if.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define IF_NAMESIZE 16
 
 struct if_nameindex

include/netdb.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
 #define __NEED_size_t

include/netinet/tcp.h

@@ -1,6 +1,8 @@
 #ifndef _NETINET_TCP_H
 #define _NETINET_TCP_H
 
+#include <features.h>
+
 #define TCP_NODELAY 1
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
 #include <sys/types.h>

include/pwd.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_size_t
 #define __NEED_uid_t
 #define __NEED_gid_t

include/sched.h

@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_struct_timespec
 #define __NEED_pid_t
 #define __NEED_time_t

include/search.h

@@ -5,12 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
-
+#include <features.h>
 
 #define __NEED_size_t
 #include <bits/alltypes.h>

include/setjmp.h

@@ -5,12 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 201112L
-#elif defined(__GNUC__)
-#define _Noreturn __attribute__((__noreturn__))
-#else
-#define _Noreturn
-#endif
+#include <features.h>
 
 #include <bits/setjmp.h>
 

include/signal.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #if defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) \
  || defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) \

include/stdio.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define __NEED_FILE
 #define __NEED_va_list

include/stdlib.h

@@ -5,18 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
-
-#if __STDC_VERSION__ >= 201112L
-#elif defined(__GNUC__)
-#define _Noreturn __attribute__((__noreturn__))
-#else
-#define _Noreturn
-#endif
+#include <features.h>
 
 #undef NULL
 #ifdef __cplusplus

include/string.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #undef NULL
 #ifdef __cplusplus

include/sys/ipc.h

@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_uid_t
 #define __NEED_gid_t
 #define __NEED_mode_t

include/sys/mman.h

@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_mode_t
 #define __NEED_size_t
 #define __NEED_off_t

include/sys/resource.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_id_t
 #define __NEED_time_t
 #define __NEED_struct_timeval

include/sys/sem.h

@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_size_t
 #define __NEED_pid_t
 #define __NEED_time_t

include/sys/sendfile.h

@@ -5,6 +5,7 @@
 extern "C" {
 #endif
 
+#include <features.h>
 #include <unistd.h>
 
 ssize_t sendfile(int, int, off_t *, size_t);

include/sys/shm.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_time_t
 #define __NEED_size_t
 #define __NEED_pid_t

include/sys/stat.h

@@ -4,11 +4,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define __NEED_dev_t
 #define __NEED_ino_t

include/sys/statfs.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #include <sys/statvfs.h>
 
 typedef struct {

include/sys/statvfs.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define __NEED_fsblkcnt_t
 #define __NEED_fsfilcnt_t

include/sys/time.h

@@ -4,11 +4,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #include <sys/select.h>
 

include/sys/types.h

@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_ino_t
 #define __NEED_dev_t
 #define __NEED_uid_t

include/sys/uio.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_size_t
 #define __NEED_ssize_t
 #define __NEED_struct_iovec

include/sys/utsname.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 struct utsname
 {
 	char sysname[65];

include/sys/wait.h

@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #include <signal.h>
 
 #define __NEED_pid_t

include/syslog.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define LOG_EMERG   0
 #define LOG_ALERT   1
 #define LOG_CRIT    2

include/termios.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_pid_t
 
 #include <bits/alltypes.h>

include/time.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #undef NULL
 #ifdef __cplusplus

include/ucontext.h

@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #include <signal.h>
 
 #ifdef _GNU_SOURCE

include/unistd.h

@@ -5,18 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
-
-#if __STDC_VERSION__ >= 201112L
-#elif defined(__GNUC__)
-#define _Noreturn __attribute__((__noreturn__))
-#else
-#define _Noreturn
-#endif
+#include <features.h>
 
 #define STDIN_FILENO  0
 #define STDOUT_FILENO 1

include/wchar.h

@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define __NEED_FILE
 #define __NEED_va_list

include/wctype.h

@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_wint_t
 #define __NEED_wctrans_t
 #define __NEED_wctype_t