strdup: Assume the function exists

[Bruno Haible]

Nowadays, all platforms have strdup - or, on native Windows, _strdup - in libc.
Testing for it at configure time is therefore obselete. This test is
complicating the support for native Windows, so I'm removing it.


2020-08-14  Bruno Haible  <bruno@clisp.org>

        strdup: Assume the function exists.
        * m4/strdup.m4 (gl_FUNC_STRDUP, gl_FUNC_STRDUP_POSIX): Don't test
        whether strdup exists.
        * modules/strdup (Files): Remove lib/strdup.c.
        (configure.ac): Don't compile strdup.c.
        * modules/strdup-posix (Depends-on, configure.ac): Don't test
        ac_cv_func_strdup.
        * doc/posix-functions/strdup.texi: Update.
        * lib/unistr/u8-strdup.c: Assume HAVE_STRDUP is 1.
        * modules/unistr/u8-strdup (Files): Remove lib/unistr/u-strdup.h.
        (Depends-on): Remove unistr/u8-strlen.

diff --git a/doc/posix-functions/strdup.texi b/doc/posix-functions/strdup.texi
index 23f49c7..2f337aa 100644
--- a/doc/posix-functions/strdup.texi
+++ b/doc/posix-functions/strdup.texi
@@ -9,8 +9,6 @@ Gnulib module: strdup or strdup-posix
 Portability problems fixed by either Gnulib module @code{strdup} or 
@code{strdup-posix}:
 @itemize
 @item
-This function is missing on some old platforms.
-@item
 This function has no prototype in @code{<string.h>} on some old platforms.
 @end itemize
 
diff --git a/lib/unistr/u8-strdup.c b/lib/unistr/u8-strdup.c
index d3b4c55..663dacb 100644
--- a/lib/unistr/u8-strdup.c
+++ b/lib/unistr/u8-strdup.c
@@ -20,21 +20,10 @@
 /* Specification.  */
 #include "unistr.h"
 
-#if HAVE_STRDUP
-
-# include <string.h>
+#include <string.h>
 
 uint8_t *
 u8_strdup (const uint8_t *s)
 {
   return (uint8_t *) strdup ((const char *) s);
 }
-
-#else
-
-# define FUNC u8_strdup
-# define UNIT uint8_t
-# define U_STRLEN u8_strlen
-# include "u-strdup.h"
-
-#endif
diff --git a/m4/strdup.m4 b/m4/strdup.m4
index 2d1fcc4..6340209 100644
--- a/m4/strdup.m4
+++ b/m4/strdup.m4
@@ -1,4 +1,4 @@
-# strdup.m4 serial 13
+# strdup.m4 serial 14
 
 dnl Copyright (C) 2002-2020 Free Software Foundation, Inc.
 
@@ -9,7 +9,6 @@ dnl with or without modifications, as long as this notice is 
preserved.
 AC_DEFUN([gl_FUNC_STRDUP],
 [
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
-  AC_CHECK_FUNCS_ONCE([strdup])
   AC_CHECK_DECLS_ONCE([strdup])
   if test $ac_cv_have_decl_strdup = no; then
     HAVE_DECL_STRDUP=0
@@ -20,11 +19,8 @@ AC_DEFUN([gl_FUNC_STRDUP_POSIX],
 [
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
   AC_REQUIRE([gl_CHECK_MALLOC_POSIX])
-  AC_CHECK_FUNCS_ONCE([strdup])
-  if test $ac_cv_func_strdup = yes; then
-    if test $gl_cv_func_malloc_posix != yes; then
-      REPLACE_STRDUP=1
-    fi
+  if test $gl_cv_func_malloc_posix != yes; then
+    REPLACE_STRDUP=1
   fi
   AC_CHECK_DECLS_ONCE([strdup])
   if test $ac_cv_have_decl_strdup = no; then
diff --git a/modules/strdup b/modules/strdup
index 619ec01..fecdc55 100644
--- a/modules/strdup
+++ b/modules/strdup
@@ -8,7 +8,6 @@ Notice:
 This module is obsolete. But you may want to use the strdup-posix module.
 
 Files:
-lib/strdup.c
 m4/strdup.m4
 
 Depends-on:
@@ -16,10 +15,6 @@ string
 
 configure.ac:
 gl_FUNC_STRDUP
-if test $ac_cv_func_strdup = no; then
-  AC_LIBOBJ([strdup])
-  gl_PREREQ_STRDUP
-fi
 gl_STRING_MODULE_INDICATOR([strdup])
 
 Makefile.am:
diff --git a/modules/strdup-posix b/modules/strdup-posix
index 846baf2..a6381f7 100644
--- a/modules/strdup-posix
+++ b/modules/strdup-posix
@@ -7,11 +7,11 @@ m4/strdup.m4
 
 Depends-on:
 string
-malloc-posix    [test $ac_cv_func_strdup = no || test $REPLACE_STRDUP = 1]
+malloc-posix    [test $REPLACE_STRDUP = 1]
 
 configure.ac:
 gl_FUNC_STRDUP_POSIX
-if test $ac_cv_func_strdup = no || test $REPLACE_STRDUP = 1; then
+if test $REPLACE_STRDUP = 1; then
   AC_LIBOBJ([strdup])
   gl_PREREQ_STRDUP
 fi
diff --git a/modules/unistr/u8-strdup b/modules/unistr/u8-strdup
index d8da47e..598adbb 100644
--- a/modules/unistr/u8-strdup
+++ b/modules/unistr/u8-strdup
@@ -3,11 +3,9 @@ Copy UTF-8 string.
 
 Files:
 lib/unistr/u8-strdup.c
-lib/unistr/u-strdup.h
 
 Depends-on:
 unistr/base
-unistr/u8-strlen
 
 configure.ac:
 AC_CHECK_FUNCS_ONCE([strdup])