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[glibc/zack/no-nested-includes] Don’t include signal.h from sys/param.h.

From: Zack Weinberg <zack at sourceware dot org>
To: glibc-cvs at sourceware dot org
Date: 18 Jun 2019 15:37:10 -0000
Subject: [glibc/zack/no-nested-includes] Don’t include signal.h from sys/param.h.
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a8394a5777c3a078565681c23015aae09feea80a

commit a8394a5777c3a078565681c23015aae09feea80a
Author: Zack Weinberg <zackw@panix.com>
Date:   Mon Jun 10 12:34:36 2019 -0400

    Donâ??t include signal.h from sys/param.h.
    
    sys/param.h is the last public header that includes signal.h.  It is
    not clear what subset of the definitions from signal.h are actually
    expected by historical users of sys/param.h; Iâ??ve chosen to take the
    comment at face value and cut it down to bits/signum.h, which supplies
    _NSIG and all of the SIG* constants.  This requires adjusting every copy
    of bits/signum.h to permit inclusion by sys/param.h as well as signal.h.
    
    While I was at it I moved the comment about sys/param.h being obsolete
    from sysdeps/mach/hurd/bits/param.h, where itâ??s not likely to be seen,
    to the top-level sys/param.h, and edited it to give more useful advice.
    
    bits/procfs.h ceased to include signal.h as of several patches ago but
    I didnâ??t realize Iâ??d done that until now.
    
    	* misc/sys/param.h: Include bits/signum.h, not signal.h.
    	Add comment explaining that this header is obsolete, based on
    	a similar comment in Hurd bits/param.h.
    
    	* bits/param.h: Add multiple inclusion guard and defensive #error.
    	* sysdeps/mach/hurd/bits/param.h: Add multiple inclusion guard.
    	Remove comment explaining that this header is obsolete (see above).
    	* sysdeps/mach/i386/bits/mach/param.h: Add multiple inclusion guard.
    	* sysdeps/unix/sysv/linux/bits/param.h: Add multiple inclusion guard.
    
    	* bits/signum-generic.h, bits/signum.h
    	* sysdeps/unix/bsd/bits/signum.h
    	* sysdeps/unix/sysv/linux/alpha/bits/signum.h
    	* sysdeps/unix/sysv/linux/bits/signum.h
    	* sysdeps/unix/sysv/linux/hppa/bits/signum.h
    	* sysdeps/unix/sysv/linux/mips/bits/signum.h:
    	Allow inclusion by sys/param.h as well as signal.h.
    
    	* scripts/check-obsolete-constructs.py (HEADER_ALLOWED_INCLUDES):
    	Update.

Diff:
---
 bits/param.h                                |  7 +++++++
 bits/signum-generic.h                       |  2 +-
 bits/signum.h                               |  2 +-
 misc/sys/param.h                            |  8 +++++++-
 scripts/check-obsolete-constructs.py        |  5 ++---
 sysdeps/mach/hurd/bits/param.h              | 13 ++++++-------
 sysdeps/mach/i386/bits/mach/param.h         |  5 +++++
 sysdeps/unix/bsd/bits/signum.h              |  2 +-
 sysdeps/unix/sysv/linux/alpha/bits/signum.h |  2 +-
 sysdeps/unix/sysv/linux/bits/param.h        |  5 +++++
 sysdeps/unix/sysv/linux/bits/signum.h       |  2 +-
 sysdeps/unix/sysv/linux/hppa/bits/signum.h  |  2 +-
 sysdeps/unix/sysv/linux/mips/bits/signum.h  |  2 +-
 sysdeps/unix/sysv/linux/sparc/bits/signum.h |  2 +-
 14 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/bits/param.h b/bits/param.h
index e83f60f..44c8505 100644
--- a/bits/param.h
+++ b/bits/param.h
@@ -16,6 +16,9 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#ifndef _BITS_PARAM_H
+#define _BITS_PARAM_H 1
+
 #ifndef _SYS_PARAM_H
 # error "Never use <bits/param.h> directly; include <sys/param.h> instead."
 #endif
@@ -31,3 +34,7 @@
 
         EXEC_PAGESIZE
 */
+
+#error "Generic bits/param.h should not have been used."
+
+#endif
diff --git a/bits/signum-generic.h b/bits/signum-generic.h
index 6fbbf20..71308d6 100644
--- a/bits/signum-generic.h
+++ b/bits/signum-generic.h
@@ -19,7 +19,7 @@
 #ifndef	_BITS_SIGNUM_GENERIC_H
 #define _BITS_SIGNUM_GENERIC_H 1
 
-#ifndef _SIGNAL_H
+#if !defined _SIGNAL_H && !defined _SYS_PARAM_H
 #error "Never include <bits/signum-generic.h> directly; use <signal.h> instead."
 #endif
 
diff --git a/bits/signum.h b/bits/signum.h
index 8c788c8..90e13c9 100644
--- a/bits/signum.h
+++ b/bits/signum.h
@@ -19,7 +19,7 @@
 #ifndef _BITS_SIGNUM_H
 #define _BITS_SIGNUM_H 1
 
-#ifndef _SIGNAL_H
+#if !defined _SIGNAL_H && !defined _SYS_PARAM_H
 #error "Never include <bits/signum.h> directly; use <signal.h> instead."
 #endif
 
diff --git a/misc/sys/param.h b/misc/sys/param.h
index bb6478f..1dedc69 100644
--- a/misc/sys/param.h
+++ b/misc/sys/param.h
@@ -16,6 +16,12 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This header is provided only for compatibility with historic Unix
+   systems.  New programs should use some combination of <endian.h>,
+   <limits.h>, <signal.h>, <stddef.h>, <stdint.h>, and <sys/types.h>
+   instead, and the names defined in those headers.  The utility
+   macros at the end of this header should not be used at all.  */
+
 #ifndef _SYS_PARAM_H
 #define _SYS_PARAM_H    1
 
@@ -24,7 +30,7 @@
 #include <sys/types.h>
 #include <limits.h>
 #include <endian.h>                     /* Define BYTE_ORDER et al.  */
-#include <signal.h>                     /* Define NSIG.  */
+#include <bits/signum.h>                /* Define NSIG.  */
 #include <bits/NULL.h>
 
 /* This file defines some things in system-specific ways.  */
diff --git a/scripts/check-obsolete-constructs.py b/scripts/check-obsolete-constructs.py
index 6c916fb..3765c57 100755
--- a/scripts/check-obsolete-constructs.py
+++ b/scripts/check-obsolete-constructs.py
@@ -573,8 +573,7 @@ HEADER_ALLOWED_INCLUDES = {
     "sys/ioctl.h":                 [ "sys/ttydefaults.h" ],
     "sys/mount.h":                 [ "sys/ioctl.h" ],
     "sys/mtio.h":                  [ "sys/ioctl.h" ],
-    "sys/param.h":                 [ "endian.h", "limits.h", "signal.h",
-                                     "sys/types.h" ],
+    "sys/param.h":                 [ "endian.h", "limits.h", "sys/types.h" ],
     "sys/procfs.h":                [ "sys/ucontext.h", "sys/user.h" ],
     "sys/ptrace.h":                [ "sys/ucontext.h" ],
     "sys/raw.h":                   [ "sys/ioctl.h" ],
@@ -624,7 +623,7 @@ HEADER_ALLOWED_INCLUDES = {
     "features.h":                  [ "gnu/stubs.h", "stdc-predef.h",
                                      "sys/cdefs.h" ],
 
-    "bits/procfs.h":               [ "signal.h", "sys/ucontext.h" ],
+    "bits/procfs.h":               [ "sys/ucontext.h" ],
 
     "bits/types/__va_list.h":      [ "stdarg.h" ],
     "bits/types/ptrdiff_t.h":      [ "stddef.h" ],
diff --git a/sysdeps/mach/hurd/bits/param.h b/sysdeps/mach/hurd/bits/param.h
index a0162e9..09485f1 100644
--- a/sysdeps/mach/hurd/bits/param.h
+++ b/sysdeps/mach/hurd/bits/param.h
@@ -16,19 +16,16 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#ifndef _BITS_PARAM_H
+#define _BITS_PARAM_H 1
+
 #ifndef _SYS_PARAM_H
 # error "Never use <bits/param.h> directly; include <sys/param.h> instead."
 #endif
 
 #include <bits/mach/param.h>
 
-/* This file is deprecated and is provided only for compatibility with
-   Unix systems.  It is unwise to include this file on programs which
-   are intended only for GNU systems.
-
-   Parts from:
-
- * Copyright (c) 1982, 1986, 1989 The Regents of the University of California.
+/* Copyright (c) 1982, 1986, 1989 The Regents of the University of California.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -85,3 +82,5 @@
 
 #define	FSHIFT	11		/* Bits to right of fixed binary point.  */
 #define FSCALE	(1<<FSHIFT)
+
+#endif /* bits/param.h */
diff --git a/sysdeps/mach/i386/bits/mach/param.h b/sysdeps/mach/i386/bits/mach/param.h
index 09a549d..3fbe86a 100644
--- a/sysdeps/mach/i386/bits/mach/param.h
+++ b/sysdeps/mach/i386/bits/mach/param.h
@@ -16,6 +16,9 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#ifndef _BITS_MACH_PARAM_H
+#define _BITS_MACH_PARAM_H 1
+
 #ifndef _SYS_PARAM_H
 # error "Never use <bits/mach/param.h> directly; include <sys/param.h> instead."
 #endif
@@ -23,3 +26,5 @@
 #ifndef EXEC_PAGESIZE
 #define EXEC_PAGESIZE	4096
 #endif
+
+#endif
diff --git a/sysdeps/unix/bsd/bits/signum.h b/sysdeps/unix/bsd/bits/signum.h
index 7e3df32..e0178e9 100644
--- a/sysdeps/unix/bsd/bits/signum.h
+++ b/sysdeps/unix/bsd/bits/signum.h
@@ -19,7 +19,7 @@
 #ifndef _BITS_SIGNUM_H
 #define _BITS_SIGNUM_H 1
 
-#ifndef _SIGNAL_H
+#if !defined _SIGNAL_H && !defined _SYS_PARAM_H
 #error "Never include <bits/signum.h> directly; use <signal.h> instead."
 #endif
 
diff --git a/sysdeps/unix/sysv/linux/alpha/bits/signum.h b/sysdeps/unix/sysv/linux/alpha/bits/signum.h
index da4ff93..4355d35 100644
--- a/sysdeps/unix/sysv/linux/alpha/bits/signum.h
+++ b/sysdeps/unix/sysv/linux/alpha/bits/signum.h
@@ -19,7 +19,7 @@
 #ifndef _BITS_SIGNUM_H
 #define _BITS_SIGNUM_H 1
 
-#ifndef _SIGNAL_H
+#if !defined _SIGNAL_H && !defined _SYS_PARAM_H
 #error "Never include <bits/signum.h> directly; use <signal.h> instead."
 #endif
 
diff --git a/sysdeps/unix/sysv/linux/bits/param.h b/sysdeps/unix/sysv/linux/bits/param.h
index 53c0f9f..f847c51 100644
--- a/sysdeps/unix/sysv/linux/bits/param.h
+++ b/sysdeps/unix/sysv/linux/bits/param.h
@@ -16,6 +16,9 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#ifndef _BITS_PARAM_H
+#define _BITS_PARAM_H 1
+
 #ifndef _SYS_PARAM_H
 # error "Never use <bits/param.h> directly; include <sys/param.h> instead."
 #endif
@@ -40,3 +43,5 @@
    and NCARGS anyway.  */
 #define NOFILE		256
 #define	NCARGS		131072
+
+#endif /* bits/param.h */
diff --git a/sysdeps/unix/sysv/linux/bits/signum.h b/sysdeps/unix/sysv/linux/bits/signum.h
index 25b0d2a..86fde6a 100644
--- a/sysdeps/unix/sysv/linux/bits/signum.h
+++ b/sysdeps/unix/sysv/linux/bits/signum.h
@@ -19,7 +19,7 @@
 #ifndef _BITS_SIGNUM_H
 #define _BITS_SIGNUM_H 1
 
-#ifndef _SIGNAL_H
+#if !defined _SIGNAL_H && !defined _SYS_PARAM_H
 #error "Never include <bits/signum.h> directly; use <signal.h> instead."
 #endif
 
diff --git a/sysdeps/unix/sysv/linux/hppa/bits/signum.h b/sysdeps/unix/sysv/linux/hppa/bits/signum.h
index c643626..5959966 100644
--- a/sysdeps/unix/sysv/linux/hppa/bits/signum.h
+++ b/sysdeps/unix/sysv/linux/hppa/bits/signum.h
@@ -19,7 +19,7 @@
 #ifndef _BITS_SIGNUM_H
 #define _BITS_SIGNUM_H 1
 
-#ifndef _SIGNAL_H
+#if !defined _SIGNAL_H && !defined _SYS_PARAM_H
 #error "Never include <bits/signum.h> directly; use <signal.h> instead."
 #endif
 
diff --git a/sysdeps/unix/sysv/linux/mips/bits/signum.h b/sysdeps/unix/sysv/linux/mips/bits/signum.h
index 89a63e4..1a430c1 100644
--- a/sysdeps/unix/sysv/linux/mips/bits/signum.h
+++ b/sysdeps/unix/sysv/linux/mips/bits/signum.h
@@ -19,7 +19,7 @@
 #ifndef _BITS_SIGNUM_H
 #define _BITS_SIGNUM_H 1
 
-#ifndef _SIGNAL_H
+#if !defined _SIGNAL_H && !defined _SYS_PARAM_H
 #error "Never include <bits/signum.h> directly; use <signal.h> instead."
 #endif
 
diff --git a/sysdeps/unix/sysv/linux/sparc/bits/signum.h b/sysdeps/unix/sysv/linux/sparc/bits/signum.h
index ec746fe..866a1c3 100644
--- a/sysdeps/unix/sysv/linux/sparc/bits/signum.h
+++ b/sysdeps/unix/sysv/linux/sparc/bits/signum.h
@@ -19,7 +19,7 @@
 #ifndef _BITS_SIGNUM_H
 #define _BITS_SIGNUM_H 1
 
-#ifndef _SIGNAL_H
+#if !defined _SIGNAL_H && !defined _SYS_PARAM_H
 #error "Never include <bits/signum.h> directly; use <signal.h> instead."
 #endif
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