Remove Wundef warnings for specification macros

This patch adds a file posix-conf-vars.list that is used to generate
macros to determine if a macro is defined as set, unset or not
defined.  gen-posix-conf-vars.awk processes this file and generates a
header (posix-conf-vars-def.h) with these macros.  A new header
posix-conf-vars.h includes this generated header and defines accessor
macros for the generated macros.

Tested on x86_64.

	* posix/Makefile (before-compile): Add posix-conf-vars-def.h.
	($(objpfx)posix-conf-vars-def.h): New target.
	* posix/posix-conf-vars.list: New file.
	* posix/posix-conf-vars.h: New file.
	* posix/confstr.c: Include posix-conf-vars.h.
	(confstr): Use CONF_IS_* macros.
	* posix/posix-envs.def: Include posix-conf-vars.h.  Use
	CONF_IS_* macros.
	* scripts/gen-posix-conf-vars.awk: New file.

1 files changed, 61 insertions, 0 deletions

diff --git a/scripts/gen-posix-conf-vars.awk b/scripts/gen-posix-conf-vars.awk
new file mode 100644
index 0000000000..16e20fc100
--- /dev/null
+++ b/scripts/gen-posix-conf-vars.awk
@@ -0,0 +1,61 @@
+# Generate posix-conf-vars-def.h with definitions for CONF_DEF{CONF} for each
+# configuration variable that getconf or sysconf may use.  Currently it is
+# equipped only to generate such macros for specification macros and for
+# SYSCONF macros in the _POSIX namespace.
+
+BEGIN {
+  prefix = ""
+}
+
+$1 ~ /^#/ || $0 ~ /^\s*$/ {
+  next
+}
+
+# Begin a new prefix.
+$NF == "{" {
+  type = $1
+  prefix = $2
+  next
+}
+
+$1 == "}" {
+  prefix = ""
+  type = ""
+  next
+}
+
+{
+  if (prefix == "" && type == "" && sc_prefix == "") {
+    printf ("Syntax error at %s:%d\n", FILENAME, FNR) > "/dev/stderr"
+    exit 1
+  }
+
+  # The prefix and variable names are indices and the value indicates what type
+  # of variable it is.  The possible options are:
+  # CONFSTR: A configuration string
+  # SYSCONF: A numeric value
+  # SPEC: A specification
+  conf[prefix][$1] = type
+}
+
+END {
+  print "/* AUTOGENERATED by gen-posix-conf-vars.awk.  DO NOT EDIT.  */\n"
+
+  # Generate macros that specify if a sysconf macro is defined and/or set.
+  for (p in conf) {
+    for (c in conf[p]) {
+      printf "#ifndef _%s_%s\n", p, c
+      printf "# define CONF_DEF_%s_%s CONF_DEF_UNDEFINED\n", p, c
+      # CONFSTR have string values and they are not set or unset.
+      if (conf[p][c] != "CONFSTR") {
+	printf "#else\n"
+	printf "# if _%s_%s > 0\n", p, c
+	printf "#  define CONF_DEF_%s_%s CONF_DEF_DEFINED_SET\n", p, c
+	printf "# else\n"
+	printf "#  define CONF_DEF_%s_%s CONF_DEF_DEFINED_UNSET\n", p, c
+	printf "# endif\n"
+      }
+      printf "#endif\n\n"
+    }
+  }
+}