backported setjmp/longjmp changes from v7.x branch:

Hand-picked from commits 436ad4b830 and 844cb490ab:
- setjmp.h: Only pass a frame pointer to setjmp if SEH is enabled
  This should avoid the need for clearing the frame pointer in the
  longjmp wrapper.
- crt: Use importlibs for longjmp.

Fixes setjmp/longjmp code built with -fno-asynchronous-unwind-tables
with SEH toolchains.

mingw-w64-crt/def-include/msvcrt-common.def.in

@@ -131,6 +131,8 @@ ADD_UNDERSCORE(hypot)
 ;logb
 ADD_UNDERSCORE(nextafter)
 
+longjmp
+
 #ifndef UCRTBASE
 _daylight DATA
 _timezone DATA
@@ -140,6 +142,4 @@ ADD_UNDERSCORE(timezone)
 ADD_UNDERSCORE(tzname)
 
 ADD_UNDERSCORE(vsnprintf_s)
-
-longjmp DATA
 #endif

mingw-w64-crt/lib-common/api-ms-win-crt-private-l1-1-0.def.in

@@ -1158,7 +1158,7 @@ F_I386(_seh_longjmp_unwind4@4)
 _set_purecall_handler
 _set_se_translator
 F_I386(_setjmp3)
-longjmp F_X86_ANY(DATA)
+longjmp
 memchr
 memcmp
 memcpy

mingw-w64-crt/lib-common/msvcrt.def.in

@@ -1413,7 +1413,6 @@ log F_X86_ANY(DATA)
 log10
 F_NON_I386(log10f F_X86_ANY(DATA))
 F_NON_I386(logf F_X86_ANY(DATA))
-F_ARM_ANY(longjmp)
 malloc
 mblen
 F_ARM_ANY(mbrlen)

mingw-w64-crt/lib-common/ucrtbase.def.in

@@ -2431,7 +2431,6 @@ logb
 logbf
 logbl
 F_NON_I386(logf F_X86_ANY(DATA))
-longjmp F_X86_ANY(DATA)
 lrint
 lrintf
 lrintl

mingw-w64-crt/lib-common/vcruntime140_app.def.in

@@ -80,7 +80,7 @@ F_I386(_seh_longjmp_unwind@4)
 _set_purecall_handler
 _set_se_translator
 F_I386(_setjmp3)
-longjmp F_X86_ANY(DATA)
+longjmp
 memchr
 memcmp
 memcpy

mingw-w64-crt/lib32/crtdll.def

@@ -599,7 +599,7 @@ localtime DATA
 ;_localtime32 = localtime
 log
 log10
-longjmp DATA
+longjmp
 malloc
 mblen
 mbstowcs

mingw-w64-crt/lib64/ntdll.def

@@ -1963,7 +1963,7 @@ iswxdigit
 isxdigit
 labs
 log
-longjmp DATA
+longjmp
 mbstowcs
 memchr
 memcmp

mingw-w64-crt/misc/mingw_getsp.S

@@ -29,29 +29,6 @@ __MINGW_USYMBOL(mingw_getsp):
 	ret
 #endif
 
-/* On ARM:
- * Error: cannot represent BFD_RELOC_32_PCREL relocation in this object file format
- * But anyway, nothing is needed here as libarm32/libmsvcrt.a is exporting longjmp
-  ldr ip, 1f
-  ldr pc, [pc, ip]
-  1: .long __imp_longjmp - (1b + 4)
-*/
-#if !(defined(_ARM_) || defined(__arm__) || defined(_ARM64_) || defined(__aarch64__))
-	.globl __MINGW_USYMBOL(longjmp)
-	.def	__MINGW_USYMBOL(longjmp);	.scl	2;	.type	32;	.endef
-__MINGW_USYMBOL(longjmp):
-#if defined(_AMD64_) || defined(__x86_64__)
-#ifndef __SEH__
-  xorq %rax,%rax
-  movq %rax, (%rcx)
-#endif
-  leaq __MINGW_IMP_LSYMBOL(longjmp)(%rip), %rax
-  jmpq *(%rax)
-#elif defined(_X86_) || defined(__i386__)
-  jmp *__imp__longjmp
-#endif
-#endif /* !(defined(_ARM_) || defined(__arm__)) */
-
 #if defined(_ARM_) || defined(__arm__) || defined(_ARM64_) || defined(__aarch64__)
 	.globl __MINGW_USYMBOL(__mingw_setjmp)
 	.def	__MINGW_USYMBOL(__mingw_setjmp);	.scl	2;	.type	32;	.endef

mingw-w64-headers/crt/setjmp.h

@@ -200,6 +200,8 @@ extern "C" {
 #define _JMP_BUF_DEFINED
 #endif
 
+_CRTIMP __MINGW_ATTRIB_NORETURN __attribute__ ((__nothrow__)) void __cdecl longjmp(jmp_buf _Buf,int _Value);
+
 void * __cdecl __attribute__ ((__nothrow__)) mingw_getsp (void);
 
 #if !defined(USE_NO_MINGW_SETJMP_TWO_ARGS)
@@ -217,18 +219,21 @@ void * __cdecl __attribute__ ((__nothrow__)) mingw_getsp (void);
 #      define setjmp(BUF) __mingw_setjmp((BUF))
 #      define longjmp __mingw_longjmp
   int __cdecl __attribute__ ((__nothrow__,__returns_twice__)) __mingw_setjmp(jmp_buf _Buf);
-#    else
+  __MINGW_ATTRIB_NORETURN __attribute__ ((__nothrow__)) void __mingw_longjmp(jmp_buf _Buf,int _Value);
+#    elif defined(__SEH__)
 #     if (__MINGW_GCC_VERSION < 40702)
 #      define setjmp(BUF) _setjmp((BUF), mingw_getsp())
 #     else
 #      define setjmp(BUF) _setjmp((BUF), __builtin_frame_address (0))
 #     endif
+#    else
+#     define setjmp(BUF) _setjmp((BUF), NULL)
 #    endif
   int __cdecl __attribute__ ((__nothrow__,__returns_twice__)) _setjmp(jmp_buf _Buf, void *_Ctx);
   int __cdecl __attribute__ ((__nothrow__,__returns_twice__)) _setjmp3(jmp_buf _Buf, void *_Ctx);
 #  else
 #    undef setjmp
-#    ifdef _WIN64
+#    ifdef __SEH__
 #     if (__MINGW_GCC_VERSION < 40702)
 #      define setjmp(BUF) _setjmpex((BUF), mingw_getsp())
 #      define setjmpex(BUF) _setjmpex((BUF), mingw_getsp())
@@ -252,9 +257,6 @@ void * __cdecl __attribute__ ((__nothrow__)) mingw_getsp (void);
   int __cdecl __attribute__ ((__nothrow__,__returns_twice__)) setjmp(jmp_buf _Buf);
 #endif
 
-  __MINGW_ATTRIB_NORETURN __attribute__ ((__nothrow__)) void __cdecl ms_longjmp(jmp_buf _Buf,int _Value)/* throw(...)*/;
-  __MINGW_ATTRIB_NORETURN __attribute__ ((__nothrow__)) void __cdecl longjmp(jmp_buf _Buf,int _Value);
-
 #ifdef __cplusplus
 }
 #endif