Thank you for this bug report. To properly diagnose the problem, we
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find out how to generate a backtrace, please read
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http://bugs.php.net/bugs-generating-backtrace-win32.php for Win32

Once you have generated a backtrace, please submit it to this bug
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You can reproduce the problem with the provided sample script. A backtrace is not necessary to fix the problem.

Looks Windows-only; I can't reproduce this on OS X or Linux. (Not a huge shock, given how much code is platform specific in mail()).

Also, we don't ask for backtraces for the hell of it: they genuinely are useful for crash bugs, because behaviour often varies significantly between different systems. You don't have to provide one, but not doing so diminishes the chances that someone will investigate your bug.

Yes it only happens on Windows. From what I looks (from my previous pull requests) it seems that the mail function has not been tested on Windows yet.

The pdb are matching in today's x86 snapshot and I was able to reproduce the crash with x86. The result is a more meaning stack trace:

 	php7.dll!_emalloc(unsigned int size) Line 2200	C
>	php7.dll!lex_scan(_zval_struct * zendlval) Line 1919	C
 	php7.dll!zendlex(_zend_parser_stack_elem * elem) Line 1382	C
 	php7.dll!zendparse() Line 4341	C
 	php7.dll!compile_file(_zend_file_handle * file_handle, int type) Line 592	C
 	php7.dll!phar_compile_file(_zend_file_handle * file_handle, int type) Line 3311	C
 	php_opcache.dll!compile_and_cache_file(_zend_file_handle * file_handle, int type, char * key, unsigned int key_length, _zend_op_array * * op_array_p, int * from_shared_memory) Line 1392	C
 	php_opcache.dll!persistent_compile_file(_zend_file_handle * file_handle, int type) Line 1611	C
 	php7.dll!compile_filename(int type, _zval_struct * filename) Line 640	C
 	php7.dll!ZEND_INCLUDE_OR_EVAL_SPEC_CV_HANDLER(_zend_execute_data * execute_data) Line 24729	C
 	php7.dll!execute_ex(_zend_execute_data * execute_data) Line 352	C
 	php7.dll!zend_call_function(_zend_fcall_info * fci, _zend_fcall_info_cache * fci_cache) Line 847	C
 	php7.dll!zend_call_method(_zval_struct * object, _zend_class_entry * obj_ce, _zend_function * * fn_proxy, const char * function_name, unsigned int function_name_len, _zval_struct * retval_ptr, int param_count, _zval_struct * arg1, _zval_struct * arg2) Line 101	C
 	php7.dll!zif_spl_autoload_call(_zend_execute_data * execute_data, _zval_struct * return_value) Line 426	C
 	php7.dll!zend_call_function(_zend_fcall_info * fci, _zend_fcall_info_cache * fci_cache) Line 866	C
 	php7.dll!zend_lookup_class_ex(_zend_string * name, const _zval_struct * key, int use_autoload) Line 1029	C
 	php7.dll!zend_fetch_class_by_name(_zend_string * class_name, const _zval_struct * key, int fetch_type) Line 1343	C
 	php7.dll!ZEND_NEW_SPEC_CONST_HANDLER(_zend_execute_data * execute_data) Line 2881	C
 	php7.dll!execute_ex(_zend_execute_data * execute_data) Line 352	C
 	php7.dll!zend_call_function(_zend_fcall_info * fci, _zend_fcall_info_cache * fci_cache) Line 847	C
 	php7.dll!zif_call_user_func(_zend_execute_data * execute_data, _zval_struct * return_value) Line 4725	C
 	php7.dll!ZEND_DO_FCALL_BY_NAME_SPEC_HANDLER(_zend_execute_data * execute_data) Line 649	C
 	php7.dll!execute_ex(_zend_execute_data * execute_data) Line 352	C
 	php7.dll!zend_call_function(_zend_fcall_info * fci, _zend_fcall_info_cache * fci_cache) Line 847	C
 	php7.dll!zif_call_user_func(_zend_execute_data * execute_data, _zval_struct * return_value) Line 4725	C
 	php7.dll!ZEND_DO_FCALL_BY_NAME_SPEC_HANDLER(_zend_execute_data * execute_data) Line 649	C
 	php7.dll!execute_ex(_zend_execute_data * execute_data) Line 352	C
 	php7.dll!zend_execute(_zend_op_array * op_array, _zval_struct * return_value) Line 381	C
 	php7.dll!zend_execute_scripts(int type, _zval_struct * retval, int file_count, ...) Line 1310	C
 	php7.dll!php_execute_script(_zend_file_handle * primary_file) Line 2527	C
 	php-cgi.exe!main(int argc, char * * argv) Line 2439	C
 	php-cgi.exe!__tmainCRTStartup() Line 536	C
 	kernel32.dll!@BaseThreadInitThunk@12()	Unknown
 	ntdll.dll!__RtlUserThreadStart()	Unknown
 	ntdll.dll!__RtlUserThreadStart@8()	Unknown

I have sent the dump by email as well.

Please disregard the last comment. It should have posted to another bug id.