Remove HAVE_ERRNO_H

The `<errno.h>` header file is part of the standard C89 headers [1] and
on older systems there needed to be also a manual check if header is
present.

Since libgd requires at least C89 or greater, the `HAVE_ERRNO_H`
symbol defined by Autoconf in configure.ac [2], and Cmake build system
files can be removed and simplifed.

Refs:
[1] https://port70.net/~nsz/c/c89/c89-draft.html#4.1.3
[2] https://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/headers.m4

8 files changed, 6 insertions, 22 deletions

diff --git a/VMS/CONFIGURE.COM b/VMS/CONFIGURE.COM
index f9a93ab..a16e021 100644
--- a/VMS/CONFIGURE.COM
+++ b/VMS/CONFIGURE.COM
@@ -857,11 +857,6 @@ $COPY SYS$INPUT [.SRC]CONFIG.H
 /* Define to 1 if you have the <dlfcn.h> header file. */
 #define HAVE_DLFCN_H 1
 
-/* Define to 1 if you have the <errno.h> header file. */
-#define HAVE_ERRNO_H 1
-
-
-
 /* Define to 1 if you have the <inttypes.h> header file. */
 #define HAVE_INTTYPES_H 1
 
diff --git a/cmake/modules/AC_HEADER_STDC.cmake b/cmake/modules/AC_HEADER_STDC.cmake
index d3775ea..3f43daa 100644
--- a/cmake/modules/AC_HEADER_STDC.cmake
+++ b/cmake/modules/AC_HEADER_STDC.cmake
@@ -1,7 +1,6 @@
 # Keep in sync with AC_CHECK_HEADERS in configure.ac.
 
 check_include_files(dirent.h HAVE_DIRENT_H)
-check_include_files(errno.h HAVE_ERRNO_H)
 check_include_files(inttypes.h HAVE_INTTYPES_H)
 check_include_files(limits.h HAVE_LIMITS_H)
 check_include_files(stddef.h HAVE_STDDEF_H)
diff --git a/configure.ac b/configure.ac
index bdd7a74..db5db52 100644
--- a/configure.ac
+++ b/configure.ac
@@ -60,7 +60,6 @@ dnl Keep in sync with cmake/modules/AC_HEADER_STDC.cmake.
 AC_HEADER_STDC
 AC_CHECK_HEADERS_ONCE(m4_flatten([
 	dirent.h
-	errno.h
 	inttypes.h
 	limits.h
 	stddef.h
diff --git a/docs/README.JPN b/docs/README.JPN
index c623cb1..220a013 100644
--- a/docs/README.JPN
+++ b/docs/README.JPN
@@ -24,7 +24,7 @@ SJIS encoding のフォントが使用できます。
 
 漢字コードの変換に OS 付属の iconv() を使う場合は
 CFLAGS に -DHAVE_ICONV を付けてコンパイルしてください。
-この場合に -DHAVE_STDARG_H と -DHAVE_ERRNO_H も付けておくと
+この場合に -DHAVE_STDARG_H と も付けておくと
 漢字コード変換の際にエラーが発生した場合に適切なメッセージを
 表示するようになります。
 
diff --git a/src/config.h.cmake b/src/config.h.cmake
index 39a46ba..ece37e3 100644
--- a/src/config.h.cmake
+++ b/src/config.h.cmake
@@ -12,9 +12,6 @@
 /* Define to 1 if you have the <dlfcn.h> header file. */
 #cmakedefine HAVE_DLFCN_H
 
-/* Define to 1 if you have the <errno.h> header file. */
-#cmakedefine HAVE_ERRNO_H
-
 /* Define if you have the ft2build.h header. */
 #cmakedefine HAVE_FT2BUILD_H
 
diff --git a/src/gdkanji.c b/src/gdkanji.c
index 93380d8..9c8fd11 100644
--- a/src/gdkanji.c
+++ b/src/gdkanji.c
@@ -11,11 +11,7 @@
 #include "gd.h"
 #include "gdhelpers.h"
 #include "gd_errors.h"
-
-#ifdef HAVE_ERRNO_H
 #include <errno.h>
-#endif
-
 #include <stdarg.h>
 #if defined(HAVE_ICONV_H)
 #include <iconv.h>
@@ -344,10 +340,10 @@ do_convert (unsigned char **to_p, const unsigned char **from_p, const char *code
 
 	if ((cd = iconv_open (EUCSTR, code)) == (iconv_t) - 1) {
 		gd_error ("iconv_open() error");
-#ifdef HAVE_ERRNO_H
+
 		if (errno == EINVAL)
 			gd_error ("invalid code specification: \"%s\" or \"%s\"", EUCSTR, code);
-#endif
+
 		ustrcpy (to, from);
 		return;
 	}
@@ -357,7 +353,7 @@ do_convert (unsigned char **to_p, const unsigned char **from_p, const char *code
 
 	if ((int) (iconv (cd, (char **)from_p, &from_len, (char **)to_p, &to_len))
 	        == -1) {
-#ifdef HAVE_ERRNO_H
+
 		if (errno == EINVAL)
 			gd_error ("invalid end of input string");
 		else if (errno == EILSEQ)
@@ -365,7 +361,7 @@ do_convert (unsigned char **to_p, const unsigned char **from_p, const char *code
 		else if (errno == E2BIG)
 			gd_error ("output buffer overflow at do_convert()");
 		else
-#endif
+
 			gd_error ("something happen");
 		ustrcpy (to, from);
 		return;
diff --git a/src/webpng.c b/src/webpng.c
index 2dff832..f7a97ec 100644
--- a/src/webpng.c
+++ b/src/webpng.c
@@ -4,9 +4,7 @@
 
 /* Bring in standard I/O and string manipulation functions */
 #include <stdarg.h>
-#ifdef HAVE_ERRNO_H
 #include <errno.h>
-#endif
 #include <stdio.h>
 #ifdef HAVE_STDLIB_H
 #include <stdlib.h>
diff --git a/windows/msys/Makefile b/windows/msys/Makefile
index 3af2faa..c502d80 100644
--- a/windows/msys/Makefile
+++ b/windows/msys/Makefile
@@ -7,7 +7,7 @@
 LIBVER=3.0.1
 
 # Misc. config flags.
-CDEFS=-DHAVE_ERRNO_H -DHAVE_ICONV -DHAVE_ICONV_H		\
+CDEFS=-DHAVE_ICONV -DHAVE_ICONV_H		\
 -DHAVE_ICONV_T_DEF -DHAVE_INTTYPES_H -DHAVE_LIMITS_H -DHAVE_STDDEF_H	\
 -DHAVE_STDINT_H -DHAVE_STDLIB_H -DHAVE_VISIBILITY -DICONV_CONST