start on makefile and fixing warnings and errors

Signed-off-by: Mattias Andrée <maandree@operamail.com>

10 files changed, 132 insertions, 96 deletions

diff --git a/include/assert.h b/include/assert.h
index 6315ae1..838a9bf 100644
--- a/include/assert.h
+++ b/include/assert.h
@@ -56,7 +56,7 @@
 #define static_assert _Static_assert
 
 
-#ifndef __PORTABLE
+#if (defined(_SLIBC_SOURCE) || defined(_GNU_SOURCE)) && !defined(__PORTABLE)
 /**
  * Unless `NDEBUG` is defined, print an error message
  * and abort the process, if `errnum` is non-zero.
@@ -65,15 +65,15 @@
  * 
  * `assert_perror` is a GNU extension.
  */
-#if defined(_SLIBC_SOURCE) || defined(_GNU_SOURCE)
-#ifdef assert_perror
-# undef assert_perror
-#endif
-#ifdef NDEBUG
-# define assert_perror(errnum)  ((void)0)
-#else
-# define assert_perror(errnum)  \
+# ifdef assert_perror
+#  undef assert_perror
+# endif
+# ifdef NDEBUG
+#  define assert_perror(errnum)  ((void)0)
+# else
+#  define assert_perror(errnum)  \
   ((void)((errnum == 0) ? 0 : (__assert_fail(NULL, errnum, __FILE__, __LINE__, __func__), 0)))
+# endif
 #endif
 
 
@@ -89,7 +89,6 @@
  */
 void __assert_fail(const char*, int, const char*, int, const char*)
   __noreturn __GCC_ONLY(__attribute__((nonnull(3, 4, 5))));
-#endif
 
 
 
diff --git a/include/bits/types.h b/include/bits/types.h
index e594e44..7a2244e 100644
--- a/include/bits/types.h
+++ b/include/bits/types.h
@@ -32,7 +32,7 @@
 #ifndef __MAX_OF
 # define  __MAX_OF(type)  \
   (((type)1) << sizeof(type))
-#define
+#endif
 
 
 /**
diff --git a/include/ctype.h b/include/ctype.h
index f01ad57..f98705d 100644
--- a/include/ctype.h
+++ b/include/ctype.h
@@ -35,7 +35,8 @@
  * @return     Whether the character is in
  *             ['0', '9'], ['A', 'Z'], or ['a', 'z'].
  */
-int (isalnum)(int);  /* [0x30, 0x39], [0x41, 0x5A], [0x61, 0x7A] */
+int (isalnum)(int)  /* [0x30, 0x39], [0x41, 0x5A], [0x61, 0x7A] */
+  __GCC_ONLY(__attribute__((const)));
 #if defined (__GNUC__)
 # define isalnum(c)  \
   ({ int __c = (c); (isalpha(__c) || isdigit(__c)); })
@@ -49,7 +50,8 @@ int (isalnum)(int);  /* [0x30, 0x39], [0x41, 0x5A], [0x61, 0x7A] */
  * @return     Whether the character is in
  *             ['A', 'Z'] or ['a', 'z'].
  */
-int (isalpha)(int);  /* [0x41, 0x5A], [0x61, 0x7A] */
+int (isalpha)(int)  /* [0x41, 0x5A], [0x61, 0x7A] */
+  __GCC_ONLY(__attribute__((const)));
 #define isalpha(c)  (islower(tolower(a)))
 
 
@@ -63,7 +65,8 @@ int (isalpha)(int);  /* [0x41, 0x5A], [0x61, 0x7A] */
  * @param   c  The character.
  * @return     Whether the character is a ' ' or a '\t'.
  */
-int (isblank)(int); /* ' ', '\t' */
+int (isblank)(int) /* ' ', '\t' */
+  __GCC_ONLY(__attribute__((const)));
 # if defined(__GNUC__)
 #  define isblank(c)  \
   ({ int __c = (c); ((__c == ' ') || (__c == '\t')); })
@@ -79,7 +82,8 @@ int (isblank)(int); /* ' ', '\t' */
  * @return     Whether the character is lower than ' ',
  *             or is 0x7F.
  */
-int (iscntrl)(int);  /* [0x00, 0x1F], 0x7F */
+int (iscntrl)(int)  /* [0x00, 0x1F], 0x7F */
+  __GCC_ONLY(__attribute__((const)));
 #if defined(__GNUC__)
 # define iscntrl(c)  \
   ({ int __c = (c); (((unsigned)__c < ' ') || (c__ == 0x7F)); })
@@ -92,7 +96,8 @@ int (iscntrl)(int);  /* [0x00, 0x1F], 0x7F */
  * @param   c  The character.
  * @return     Whether the character is in ['0', '9'].
  */
-int (isdigit)(int);  /* [0x30, 0x39] */
+int (isdigit)(int)  /* [0x30, 0x39] */
+  __GCC_ONLY(__attribute__((const)));
 #define isdigit(c)  ((unsigned)((c) - '0') < 10)
 
 
@@ -103,7 +108,8 @@ int (isdigit)(int);  /* [0x30, 0x39] */
  * @return     Whether the character is greater
  *             than ' ', but is not 0x7F.
  */
-int (isgraph)(int);  /* [0x21, 0x7E] */
+int (isgraph)(int)  /* [0x21, 0x7E] */
+  __GCC_ONLY(__attribute__((const)));
 #define isgraph(c)  ((unsigned)(c - 0x21) < 0x5E)
 
 
@@ -114,7 +120,8 @@ int (isgraph)(int);  /* [0x21, 0x7E] */
  * @param   c  The character.
  * @return     Whether the character is in ['a', 'z'].
  */
-int (islower)(int);  /* [0x61, 0x7A] */
+int (islower)(int)  /* [0x61, 0x7A] */
+  __GCC_ONLY(__attribute__((const)));
 #define islower(c)  ((unsigned)((c) - 'a') < 26)
 
 
@@ -126,7 +133,8 @@ int (islower)(int);  /* [0x61, 0x7A] */
  * @return     Whether the character is at least
  *             as great as ' ', but is not 0x7F.
  */
-int (isprint)(int);  /* [0x20, 0x7E] */
+int (isprint)(int)  /* [0x20, 0x7E] */
+  __GCC_ONLY(__attribute__((const)));
 #define isprint(c)  ((unsigned)(c - 0x20) < 0x5F)
 
 
@@ -138,7 +146,8 @@ int (isprint)(int);  /* [0x20, 0x7E] */
  * @param   c  The character.
  * @return     Whether the character is a punctuation.
  */
-int (ispunct)(int);  /* isprint && !isalnum && !isspace) */
+int (ispunct)(int)  /* isprint && !isalnum && !isspace) */
+  __GCC_ONLY(__attribute__((const)));
 #if defined (__GNUC__)
 # define ispunk(c)  \
   ({ int __c = (c); (isprint(__c) && !isalnum(__c) && !isspace(__c)); })
@@ -152,7 +161,8 @@ int (ispunct)(int);  /* isprint && !isalnum && !isspace) */
  * @return     Whether the character is a ' ', '\f',
  *             '\n', '\r', '\t', or '\v'.
  */
-int (isspace)(int);  /* 0x20, [0x09, 0x0D] */
+int (isspace)(int)  /* 0x20, [0x09, 0x0D] */
+  __GCC_ONLY(__attribute__((const)));
 #if defined (__GNUC__)
 # define isspace(c)  \
   ({ int __c = (c); ((__c == ' ') || ((unsigned)(__c - '\t') < 5)); })
@@ -166,7 +176,8 @@ int (isspace)(int);  /* 0x20, [0x09, 0x0D] */
  * @param   c  The character.
  * @return     Whether the character is in ['A', 'Z'].
  */
-int (isupper)(int);  /* [0x41, 0x5A] */
+int (isupper)(int)  /* [0x41, 0x5A] */
+  __GCC_ONLY(__attribute__((const)));
 #define isupper(c)  ((unsigned)((c) - 'A') < 26)
 
 
@@ -179,7 +190,8 @@ int (isupper)(int);  /* [0x41, 0x5A] */
  * @return     Whether the character is in
  *             ['0', '9'], ['A', 'Z'], or ['a', 'z'].
  */
-int (isxdigit)(int);  /* [0x30, 0x39], [0x41, 0x46], [0x61, 0x66] */
+int (isxdigit)(int)  /* [0x30, 0x39], [0x41, 0x46], [0x61, 0x66] */
+  __GCC_ONLY(__attribute__((const)));
 #if defined (__GNUC__)
 # define isxdigit(c)  \
   ({ int __c = (c); (isdigit(__c) && (tolower(__c) - 'a' < 6)); })
@@ -201,8 +213,9 @@ int (isxdigit)(int);  /* [0x30, 0x39], [0x41, 0x46], [0x61, 0x66] */
  *             Guaranteed to be unchanged if the
  *             character already is in lowercase.
  */
-int (tolower)(int);  /* [0x41, 0x5A] -> [0x61, 0x7A] */
-#define tolower(c)  ((c) | 0x20)
+int (tolower)(int)  /* [0x41, 0x5A] -> [0x61, 0x7A] */
+  __GCC_ONLY(__attribute__((const)));
+#define tolower(c)  ((unsigned)(c) | 0x20)
 
 /**
  * Convert a lowercase ASCII character to
@@ -218,8 +231,9 @@ int (tolower)(int);  /* [0x41, 0x5A] -> [0x61, 0x7A] */
  *             Guaranteed to be unchanged if the
  *             character already is in lowercase.
  */
-int (toupper)(int);  /* [0x61, 0x7A] -> [0x41, 0x5A] */
-#define toupper(c)  ((c) & ~0x20)
+int (toupper)(int)  /* [0x61, 0x7A] -> [0x41, 0x5A] */
+  __GCC_ONLY(__attribute__((const)));
+#define toupper(c)  ((unsigned)(c) & ~0x20)
 
 
 
@@ -229,7 +243,8 @@ int (toupper)(int);  /* [0x61, 0x7A] -> [0x41, 0x5A] */
  * @param   c  The character
  * @return  -  Whether the character is an ASCII character.
  */
-int (isascii)(int);  /* [0x00, 0x7E] */
+int (isascii)(int)  /* [0x00, 0x7E] */
+  __GCC_ONLY(__attribute__((const)));
 #define isascii(c)  ((unsigned)(c) < 0x7F)
 
 /**
@@ -242,9 +257,10 @@ int (isascii)(int);  /* [0x00, 0x7E] */
  * @param  c  The character with the 8:th bit cleared.
  */
 int (toascii)(int)
-  __warning("Using 'toascii' is, generally, unwise.");
+  __warning("Using 'toascii' is, generally, unwise.")
+  __GCC_ONLY(__attribute__((const)));
 #if defined(_SLIBC_SUPPRESS_WARNINGS)
-# define toascii(c)  ((c) & 0x7F)
+# define toascii(c)  ((unsigned)(c) & 0x7F)
 #endif
 
 /**
@@ -252,14 +268,16 @@ int (toascii)(int)
  * It is provided for backwards-compatibility with SVID.
  */
 int _tolower(int)
-  __deprecated("Use 'tolower' instead.");
+  __deprecated("Use 'tolower' instead.")
+  __GCC_ONLY(__attribute__((const)));
 
 /**
  * This function is identical to `tolower`.
  * It is provided for backwards-compatibility with SVID.
  */
 int _toupper(int)
-  __deprecated("Use 'toupper' instead.");
+  __deprecated("Use 'toupper' instead.")
+  __GCC_ONLY(__attribute__((const)));
 
 
 
diff --git a/include/err.h b/include/err.h
index 6e9b828..c4b241a 100644
--- a/include/err.h
+++ b/include/err.h
@@ -87,7 +87,7 @@ void vwarnx(const char*, va_list);
  * @param  ...     Formatting-arguments.
  */
 void err(int, const char*, ...)
-  __noreturn __GCC_ONLY(__attribute__((format(printf, 2, 3))));
+  __GCC_ONLY(__attribute__((format(printf, 2, 3)))) __noreturn;
 
 /**
  * Print an error message to stderr, followed by a
diff --git a/include/error.h b/include/error.h
index f38ee44..37d8328 100644
--- a/include/error.h
+++ b/include/error.h
@@ -26,7 +26,7 @@
 #endif
 
 
-#include <slibc/features.h>
+#include <stdarg.h>
 
 
 
@@ -140,7 +140,7 @@ extern volatile int error_one_per_line;
  * 
  * This is a GNU extension.
  */
-extern volatile void (*error_print_progname)(void);
+extern void (*volatile error_print_progname)(void);
 
 
 
diff --git a/include/stddef.h b/include/stddef.h
index 26286f5..871a618 100644
--- a/include/stddef.h
+++ b/include/stddef.h
@@ -44,7 +44,7 @@
  */
 #ifndef NULL
 # define NULL  ((void*)0)
-#define
+#endif
 
 
 /**
diff --git a/include/stdlib.h b/include/stdlib.h
index 3151947..c02e094 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -39,7 +39,7 @@
  */
 #ifndef NULL
 # define NULL  ((void*)0)
-#define
+#endif
 
 
 
diff --git a/include/string.h b/include/string.h
index c43b41d..fe1b930 100644
--- a/include/string.h
+++ b/include/string.h
@@ -22,6 +22,14 @@
 
 
 
+/**
+ * `NULL`'s canonical header is <stddef.h>
+ */
+#ifndef NULL
+# define NULL  ((void*)0)
+#endif
+
+
 #define __NEED_size_t
 #define __NEED_locale_t /* TODO not defined */
 
@@ -66,11 +74,13 @@ char* strerror(int)
  *                  `LC_GLOBAL_LOCALE`, lest the behaviour is undefined.
  * @return          A description of the error.
  */
+/* TODO strerror_l
 char* strerror_l(int, locale_t)
   __GCC_ONLY(__attribute__((warn_unused_result)));
+*/
 
 
-#if !defined(__PORTABLE) && !defined(_SLIBC_SOURCE)
+#if !defined(__PORTABLE)
 /**
  * Reenterant variant of `strerror`.
  * 
@@ -125,7 +135,7 @@ char* __gnu_strerror_r(int, char*, size_t); /* GNU-specific strerror_r */
  * @return       The number of bytes before the first NUL byte.
  */
 size_t strlen(const char*)
-  __GCC_ONLY(__attribute__((nonnull, warn_unused_result)));
+  __GCC_ONLY(__attribute__((nonnull, warn_unused_result, pure)));
 
 #if (defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) || \
      defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || \
@@ -140,7 +150,7 @@ size_t strlen(const char*)
  *                  `maxlen` if no NUL byte was found.
  */
 size_t strnlen(const char*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 #endif
 
 
@@ -716,7 +726,7 @@ void* memdup(const void*, size_t)
  *                see the specifications for `a` and `b`.
  */
 int memcmp(const void*, const void*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 
 /**
  * Compare two strings alphabetically in a case sensitive manner.
@@ -727,7 +737,7 @@ int memcmp(const void*, const void*, size_t)
  *             see the specifications for `a` and `b`.
  */
 int strcmp(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Compare two strings alphabetically in a case sensitive manner.
@@ -739,12 +749,12 @@ int strcmp(const char*, const char*)
  *                  see the specifications for `a` and `b`.
  */
 int strncmp(const char*, const char*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 
 #if defined(_GNU_SOURCE) && !defined(__PORTABLE)
 int strverscmp(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 /* TODO document and implement strverscmp */
 #endif
 
@@ -759,7 +769,7 @@ int strverscmp(const char*, const char*)
  *                   `NULL` if none were found.
  */
 void* memchr(const void*, int, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 
 #if (defined(_GNU_SOURCE) || defined(_SLIBC_SOURCE)) && !defined(__PORTABLE)
 /**
@@ -773,7 +783,7 @@ void* memchr(const void*, int, size_t)
  * @return           Pointer to the first occurrence of `c`.
  */
 void* rawmemchr(const void*, int)
-  __GCC_ONLY(__attribute__((warn_unused_result, returns_nonnull, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, returns_nonnull, nonnull, pure)));
 #endif
 
 /**
@@ -790,7 +800,7 @@ void* rawmemchr(const void*, int)
  *                   `NULL` if none were found.
  */
 void* memrchr(const void*, int, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 
 /**
  * Find the first occurrence of a byte in a string.
@@ -806,7 +816,7 @@ void* memrchr(const void*, int, size_t)
  *                  `NULL` if none were found.
  */
 char* strchr(const char*, int)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 #if (defined(_GNU_SOURCE) || defined(_SLIBC_SOURCE)) && !defined(__PORTABLE)
 /**
@@ -824,7 +834,7 @@ char* strchr(const char*, int)
  *                  if none were found.
  */
 char* strchrnul(const char*, int)
-  __GCC_ONLY(__attribute__((warn_unused_result, returns_nonnull, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, returns_nonnull, nonnull, pure)));
 #endif
 
 /**
@@ -842,7 +852,7 @@ char* strchrnul(const char*, int)
  *                  `NULL` if none were found.
  */
 char* strrchr(const char*, int)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 
 /* TODO Add case insensitive character searching functions. */
@@ -858,7 +868,7 @@ char* strrchr(const char*, int)
  *                    substring, `NULL` if not found.
  */
 char* strstr(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring.
@@ -870,7 +880,7 @@ char* strstr(const char*, const char*)
  *                    substring, `NULL` if not found.
  */
 char* strcasestr(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 #if defined(_SLIBC_SOURCE) && !defined(__PORTABLE)
 /**
@@ -887,7 +897,7 @@ char* strcasestr(const char*, const char*)
  *                    substring, `NULL` if not found.
  */
 char* strnstr(const char*, const char*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring.
@@ -902,7 +912,7 @@ char* strnstr(const char*, const char*, size_t)
  *                    substring, `NULL` if not found.
  */
 char* strncasestr(const char*, const char*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring.
@@ -916,7 +926,7 @@ char* strncasestr(const char*, const char*, size_t)
  * @return            Pointer to the first occurrence of the substring.
  */
 char* rawstrstr(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, returns_nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, returns_nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring.
@@ -930,7 +940,7 @@ char* rawstrstr(const char*, const char*)
  * @return            Pointer to the first occurrence of the substring.
  */
 char* rawstrcasestr(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, returns_nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, returns_nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring
@@ -947,7 +957,7 @@ char* rawstrcasestr(const char*, const char*)
  *                           the substring, `NULL` if not found.
  */
 void* memcasemem(const void*, size_t, const void*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 #endif
 
 #if (defined(_GNU_SOURCE) || defined(_SLIBC_SOURCE)) && !defined(__PORTABLE)
@@ -966,7 +976,7 @@ void* memcasemem(const void*, size_t, const void*, size_t)
  *                           the substring, `NULL` if not found.
  */
 void* memmem(const void*, size_t, const void*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 #endif
 
 
@@ -983,7 +993,7 @@ void* memmem(const void*, size_t, const void*, size_t)
  * @return           The length of the substring.
  */
 size_t strspn(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Returns length of the initial substring
@@ -995,7 +1005,7 @@ size_t strspn(const char*, const char*)
  * @return           The length of the substring.
  */
 size_t strcspn(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * This function works like `strcspn`,
@@ -1010,7 +1020,7 @@ size_t strcspn(const char*, const char*)
  *                   `NULL` is returned if none is found.
  */
 char* stpbrk(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 
 /**
@@ -1086,7 +1096,7 @@ char* strsep(char** restrict, const char* restrict)
  *                    so it must not freed or edited.
  */
 char* __gnu_basename(const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 # define basename  __gnu_basename
 #endif
 
diff --git a/include/strings.h b/include/strings.h
index 2044fa6..a06a167 100644
--- a/include/strings.h
+++ b/include/strings.h
@@ -64,7 +64,7 @@ void bcopy(const void*, void*, size_t)
  */
 int bcmp(const void*, const void*, size_t)
   __deprecated("Use 'memcmp' instead.")
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 
 
 /**
@@ -78,7 +78,7 @@ int bcmp(const void*, const void*, size_t)
  *             see the specifications for `a` and `b`.
  */
 int strcasecmp(const char*, const char*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Compare two strings alphabetically in a case insensitive manner.
@@ -92,7 +92,7 @@ int strcasecmp(const char*, const char*)
  *                  see the specifications for `a` and `b`.
  */
 int strncasecmp(const char*, const char*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 
 /**
@@ -102,7 +102,7 @@ int strncasecmp(const char*, const char*, size_t)
  */
 char* index(const char*, int)
   __deprecated("Use 'strchr' instead.")
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * This function is identical to `strrchr`.
@@ -111,7 +111,7 @@ char* index(const char*, int)
  */
 char* rindex(const char*, int)
   __deprecated("Use 'strrchr' instead.")
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 
 
diff --git a/include/wchar.h b/include/wchar.h
index faf9275..12b1de9 100644
--- a/include/wchar.h
+++ b/include/wchar.h
@@ -23,6 +23,14 @@
 
 
 
+/**
+ * `NULL`'s canonical header is <stddef.h>
+ */
+#ifndef NULL
+# define NULL  ((void*)0)
+#endif
+
+
 #define __NEED_size_t
 #define __NEED_wchar_t
 
@@ -37,7 +45,7 @@
  *               first NUL character.
  */
 size_t wcslen(const wchar_t*)
-  __GCC_ONLY(__attribute__((nonnull, warn_unused_result)));
+  __GCC_ONLY(__attribute__((nonnull, warn_unused_result, pure)));
 
 #if (defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) || \
      defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || \
@@ -52,7 +60,7 @@ size_t wcslen(const wchar_t*)
  *                  NUL character was found.
  */
 size_t wcsnlen(const wchar_t*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 #endif
 
 
@@ -200,7 +208,7 @@ wchar_t* wcpcpy(wchar_t* restrict, const wchar_t* restrict)
  *                   one character passed the last written non-NUL
  *                   character.
  */
-wchar_t* wcsccpy(wchar_t* restrict, const wchar_t* restrict, wchat_t)
+wchar_t* wcsccpy(wchar_t* restrict, const wchar_t* restrict, wchar_t)
   __GCC_ONLY(__attribute__((nonnull)));
 
 /**
@@ -286,7 +294,7 @@ wchar_t* wcpncpy(wchar_t* restrict, const wchar_t* restrict, size_t)
  *                   one character passed the last written non-NUL
  *                   character.
  */
-wchar_t* wcscncpy(wchar_t* restrict, const wchar_t* restrict, wchat_t, size_t)
+wchar_t* wcscncpy(wchar_t* restrict, const wchar_t* restrict, wchar_t, size_t)
   __GCC_ONLY(__attribute__((nonnull)));
 
 /**
@@ -361,7 +369,7 @@ wchar_t* wcpmove(wchar_t*, const wchar_t*)
  *                   one character passed the last written non-NUL
  *                   character.
  */
-wchar_t* wcscmove(wchar_t*, const wchar_t*, wchat_t)
+wchar_t* wcscmove(wchar_t*, const wchar_t*, wchar_t)
   __GCC_ONLY(__attribute__((nonnull)));
 
 /**
@@ -446,7 +454,7 @@ wchar_t* wcpnmove(wchar_t*, const wchar_t*, size_t)
  *                   one character passed the last written non-NUL
  *                   character.
  */
-wchar_t* wcscnmove(wchar_t*, const wchar_t*, wchat_t, size_t)
+wchar_t* wcscnmove(wchar_t*, const wchar_t*, wchar_t, size_t)
   __GCC_ONLY(__attribute__((nonnull)));
 
 /**
@@ -641,7 +649,7 @@ wchar_t* wmemdup(const wchar_t*, size_t)
  *                see the specifications for `a` and `b`.
  */
 int wmemcmp(const wchar_t*, const wchar_t*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 
 /**
  * Compare two strings alphabetically in a case sensitive manner.
@@ -652,7 +660,7 @@ int wmemcmp(const wchar_t*, const wchar_t*, size_t)
  *             see the specifications for `a` and `b`.
  */
 int wcscmp(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 #if (defined(_GNU_SOURCE) || defined(_SLIBC_SOURCE)) && !defined(__PORTABLE)
 /**
@@ -668,7 +676,7 @@ int wcscmp(const wchar_t*, const wchar_t*)
  *             see the specifications for `a` and `b`.
  */
 int wcscasecmp(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Compare two strings alphabetically in a case sensitive manner.
@@ -682,7 +690,7 @@ int wcscasecmp(const wchar_t*, const wchar_t*)
  *                  see the specifications for `a` and `b`.
  */
 int wcsncmp(const wchar_t*, const wchar_t*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Compare two strings alphabetically in a case insensitive manner.
@@ -698,7 +706,7 @@ int wcsncmp(const wchar_t*, const wchar_t*, size_t)
  *                  see the specifications for `a` and `b`.
  */
 int wcsncasecmp(const wchar_t*, const wchar_t*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 #endif
 
 
@@ -713,7 +721,7 @@ int wcsncasecmp(const wchar_t*, const wchar_t*, size_t)
  *                   `NULL` if none were found.
  */
 wchar_t* wmemchr(const wchar_t*, wchar_t, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 
 #if defined(_SLIBC_SOURCE) && !defined(__PORTABLE)
 /**
@@ -728,7 +736,7 @@ wchar_t* wmemchr(const wchar_t*, wchar_t, size_t)
  * @return           Pointer to the first occurrence of `c`.
  */
 wchar_t* rawwmemchr(const wchar_t*, wchar_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, returns_nonnull, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, returns_nonnull, nonnull, pure)));
 
 /**
  * Find the last occurrence of a wide character in
@@ -747,7 +755,7 @@ wchar_t* rawwmemchr(const wchar_t*, wchar_t)
  *                   `NULL` if none were found.
  */
 wchar_t* wmemrchr(const wchar_t*, wchar_t, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 #endif
 
 /**
@@ -761,7 +769,7 @@ wchar_t* wmemrchr(const wchar_t*, wchar_t, size_t)
  *                  `NULL` if none were found.
  */
 wchar_t* wcschr(const wchar_t*, wchar_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 #if (defined(_GNU_SOURCE) || defined(_SLIBC_SOURCE)) && !defined(__PORTABLE)
 /**
@@ -780,7 +788,7 @@ wchar_t* wcschr(const wchar_t*, wchar_t)
  *                  if none were found.
  */
 wchar_t* wcschrnul(const wchar_t*, wchar_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, returns_nonnull, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, returns_nonnull, nonnull, pure)));
 #endif
 
 /**
@@ -798,7 +806,7 @@ wchar_t* wcschrnul(const wchar_t*, wchar_t)
  *                  `NULL` if none were found.
  */
 wchar_t* wcsrchr(const wchar_t*, wchar_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 
 /* TODO Add case insensitive character searching functions. */
@@ -808,7 +816,7 @@ wchar_t* wcsrchr(const wchar_t*, wchar_t)
  * This function is identical to `wcsstr`.
  */
 wchar_t* wcswcs(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)))
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)))
   __deprecated("Use 'wcsstr' instead.");
 
 /**
@@ -821,7 +829,7 @@ wchar_t* wcswcs(const wchar_t*, const wchar_t*)
  *                    substring, `NULL` if not found.
  */
 wchar_t* wcsstr(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 #if defined(_SLIBC_SOURCE) && !defined(__PORTABLE)
 /**
@@ -836,7 +844,7 @@ wchar_t* wcsstr(const wchar_t*, const wchar_t*)
  *                    substring, `NULL` if not found.
  */
 wchar_t* wcscasestr(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring.
@@ -852,7 +860,7 @@ wchar_t* wcscasestr(const wchar_t*, const wchar_t*)
  *                    substring, `NULL` if not found.
  */
 wchar_t* wcsnstr(const wchar_t*, const wchar_t*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring.
@@ -867,7 +875,7 @@ wchar_t* wcsnstr(const wchar_t*, const wchar_t*, size_t)
  *                    substring, `NULL` if not found.
  */
 wchar_t* wcsncasestr(const wchar_t*, const wchar_t*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring.
@@ -881,7 +889,7 @@ wchar_t* wcsncasestr(const wchar_t*, const wchar_t*, size_t)
  * @return            Pointer to the first occurrence of the substring.
  */
 wchar_t* rawwcsstr(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, returns_nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, returns_nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring.
@@ -895,7 +903,7 @@ wchar_t* rawwcsstr(const wchar_t*, const wchar_t*)
  * @return            Pointer to the first occurrence of the substring.
  */
 wchar_t* rawwcscasestr(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, returns_nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, returns_nonnull, pure)));
 
 /**
  * Finds the first occurrence of a substring
@@ -911,7 +919,8 @@ wchar_t* rawwcscasestr(const wchar_t*, const wchar_t*)
  * @return                   Pointer to the first occurrence of
  *                           the substring, `NULL` if not found.
  */
-wchar_t* wmemcasemem(const wchar_t*, size_t, const wchar_t*, size_t);
+wchar_t* wmemcasemem(const wchar_t*, size_t, const wchar_t*, size_t)
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 #endif
 
 #if (defined(_GNU_SOURCE) || defined(_SLIBC_SOURCE)) && !defined(__PORTABLE)
@@ -931,7 +940,7 @@ wchar_t* wmemcasemem(const wchar_t*, size_t, const wchar_t*, size_t);
  *                           the substring, `NULL` if not found.
  */
 wchar_t* wmemmem(const wchar_t*, size_t, const wchar_t*, size_t)
-  __GCC_ONLY(__attribute__((warn_unused_result)));
+  __GCC_ONLY(__attribute__((warn_unused_result, pure)));
 #endif
 
 
@@ -948,7 +957,7 @@ wchar_t* wmemmem(const wchar_t*, size_t, const wchar_t*, size_t)
  * @return           The length of the substring.
  */
 size_t wcsspn(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * Returns length of the initial substring
@@ -960,7 +969,7 @@ size_t wcsspn(const wchar_t*, const wchar_t*)
  * @return           The length of the substring.
  */
 size_t wcscspn(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 /**
  * This function works like `strcspn`,
@@ -975,7 +984,7 @@ size_t wcscspn(const wchar_t*, const wchar_t*)
  *                   `NULL` is returned if none is found.
  */
 wchar_t* wcpbrk(const wchar_t*, const wchar_t*)
-  __GCC_ONLY(__attribute__((warn_unused_result, nonnull)));
+  __GCC_ONLY(__attribute__((warn_unused_result, nonnull, pure)));
 
 
 /**