headers: stdlib.h: fix #pragma pack

`#pragma pop()` restores to "default packing" instead of "previous
packing", which can potentially cause problems and/or generate warnings.

Signed-off-by: Zhongteng Gui <dragon-archer@outlook.com>
Signed-off-by: LIU Hao <lh_mouse@126.com>

mingw-w64-crt/configure.ac

diff --git a/mingw-w64-crt/configure.ac b/mingw-w64-crt/configure.ac
index c71d1b7..dd73c33 100644
--- a/mingw-w64-crt/configure.ac
+++ b/mingw-w64-crt/configure.ac
@@ -439,15 +439,6 @@
    )
 
 saved_CFLAGS="$CFLAGS"
-AC_MSG_CHECKING([whether the compiler supports -Wpragma-pack])
-CFLAGS="$CFLAGS -Wpragma-pack"
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[]])],
-    [supports_wpragma_pack=yes],[supports_wpragma_pack=no])
-AC_MSG_RESULT([$supports_wpragma_pack])
-if test "$supports_wpragma_pack" = "yes"; then
-    ADD_C_CXX_WARNING_FLAGS="$ADD_C_CXX_WARNING_FLAGS -Wno-pragma-pack"
-fi
-CFLAGS="$saved_CFLAGS"
 AC_MSG_CHECKING([whether the compiler supports -Warray-bounds])
 CFLAGS="$CFLAGS -Warray-bounds"
 AC_COMPILE_IFELSE([AC_LANG_SOURCE([[]])],

mingw-w64-crt/math/DFP/dfp_internal.h

diff --git a/mingw-w64-crt/math/DFP/dfp_internal.h b/mingw-w64-crt/math/DFP/dfp_internal.h
index 32d81ce..4408037 100644
--- a/mingw-w64-crt/math/DFP/dfp_internal.h
+++ b/mingw-w64-crt/math/DFP/dfp_internal.h
@@ -117,7 +117,7 @@
 
 */
 
-#include <pshpack1.h>
+#pragma pack(push, 1)
 #ifdef __GNUC__
 #define structpack __attribute__((gcc_struct))
 #else
@@ -202,7 +202,7 @@
 typedef type0d128 _Decimal128;
 #endif /* _MSC_VER */
 
-#include <poppack.h>
+#pragma pack(pop)
 
 typedef union ud32 {
   _Decimal32 d;

mingw-w64-crt/stdio/mingw_pformat.c

diff --git a/mingw-w64-crt/stdio/mingw_pformat.c b/mingw-w64-crt/stdio/mingw_pformat.c
index 84e62f5..2bbe520 100644
--- a/mingw-w64-crt/stdio/mingw_pformat.c
+++ b/mingw-w64-crt/stdio/mingw_pformat.c
@@ -84,7 +84,7 @@
  * is better to just keep these definitions here.
  */
 
-#include <pshpack1.h>
+#pragma pack(push, 1)
 /* workaround gcc bug */
 #if defined(__GNUC__) && !defined(__clang__)
 #define ATTRIB_GCC_STRUCT __attribute__((gcc_struct))
@@ -103,7 +103,7 @@
   __tI128 t128;
   __tI128_2 t128_2;
 } __uI128;
-#include <poppack.h>
+#pragma pack(pop)
 
 #ifndef _VALUES_H
 /*

mingw-w64-headers/crt/stdlib.h

diff --git a/mingw-w64-headers/crt/stdlib.h b/mingw-w64-headers/crt/stdlib.h
index 3962822..c4c2ff0 100644
--- a/mingw-w64-headers/crt/stdlib.h
+++ b/mingw-w64-headers/crt/stdlib.h
@@ -39,11 +39,11 @@
 #ifndef _CRT_DOUBLE_DEC
 #define _CRT_DOUBLE_DEC
 
-#pragma pack(4)
+#pragma pack(push, 4)
   typedef struct {
     unsigned char ld[10];
   } _LDOUBLE;
-#pragma pack()
+#pragma pack(pop)
 
 #define _PTR_LD(x) ((unsigned char *)(&(x)->ld))
 
@@ -64,11 +64,11 @@
 
 #pragma pop_macro("long")
 
-#pragma pack(4)
+#pragma pack(push, 4)
   typedef struct {
     unsigned char ld12[12];
   } _LDBL12;
-#pragma pack()
+#pragma pack(pop)
 #endif
 
 #define RAND_MAX 0x7fff