Avoid uses of zend_string_dup/zend_string_copy when it will outlive the http request

Related to #255 and #247

I stopped using registerExtension, but I think there might be one more registerExtension bug anyway, or even non-obvious bugs.

From MSHUTDOWN_FUNCTION, the only thing I can think of that would leak are extensions and their associated data (e.g. deps).

Motivation for suggesting switching all uses of zend_string_dup/zend_string_copy to zend_string_init() instead

I don't expect copying strings vs adding references to be a large source of extra memory usage for v8js.
If this crashes or misbehaves (e.g. frees a string twice, or too early, or not at all), it would be easier to narrow down the cause when running with VALGRIND.
Interned or temporary strings can cause problem if they're persisted by v8js beyond the lifetime of a request.

» grep -E 'zend_string_(copy|dup)' *.cc *.h
v8js_class.cc:  Z_STR_P(p) = zend_string_dup(Z_STR_P(p), 1);
v8js_class.cc:  // (zend_string_dup would return the original interned string, if interned, so we don't use that)
v8js_v8object_class.cc:                 f->common.function_name = zend_string_copy(method);
v8js_variables.cc:        ctx->variable_name = zend_string_copy(Z_STR_P(item));

One use from registerExtension with an array of deps seems like it might also be a problem for non-ZTS builds.

Because of that, zend_persistent_zval_dup should probably use zend_string_init instead. zend_string_dup() will return the original pointer for interned strings (e.g. in php 7.2)

    // Allocate a persistent string which will survive until module shutdown on both ZTS(Persistent) and NTS(Not interned, those would be cleaned up)
    // (zend_string_dup would return the original interned string, if interned, so we don't use that)
    jsext->name = zend_string_init(ZSTR_VAL(name), ZSTR_LEN(name), 1);
    jsext->source = zend_string_init(ZSTR_VAL(source), ZSTR_LEN(source), 1);

    if (jsext->deps) {
        jsext->deps_ht = (HashTable *) malloc(sizeof(HashTable));
        zend_hash_init(jsext->deps_ht, jsext->deps_count, NULL, v8js_persistent_zval_dtor, 1);
        zend_hash_copy(jsext->deps_ht, Z_ARRVAL_P(deps_arr), v8js_persistent_zval_ctor);
    }

Context for why I'm looking at string copying in V8js (if anyone has similar issues): I'm seeing a segfault in zend_interned_string_find_permanent in long-running httpd processes for a fraction of apache restarts (if I read the instruction pointer correctly).

I'm not using registerExtension anywhere
I'm using php 7.2.24 and v8js 2.1.0. Some opcache bugs were fixed in 7.2.25 and 7.3, but they all seem unrelated.
The code in question uses V8Js with instance properties that are strings, PHP closures with use($var), etc.
Some V8js instances execute multiple scripts, then have methods invoked multiple times. I haven't obtained a core dump yet. Rolling back V8js seems to have helped in 7.1
This happens with opcache enabled, and with/without xdebug
There are two apache(httpd) pools - the segfault only seems to happen during restarts after the second pool gets stopped, not the first. This might be a coincidence.

zend_interned_string_find_permanent seems like it would only get called by opcache in php 7.2. The line it crashes on suggests that the pointer to the zend_string that is being looked up was corrupted.

0000000000474110 <zend_interned_string_find_permanent>:
  474110:       41 57                   push   %r15
  474112:       49 89 ff                mov    %rdi,%r15
  474115:       41 56                   push   %r14
  474117:       41 55                   push   %r13
  474119:       41 54                   push   %r12
  47411b:       55                      push   %rbp
  47411c:       53                      push   %rbx
  47411d:       48 83 ec 08             sub    $0x8,%rsp
  474121:       48 8b 6f 08             mov    0x8(%rdi),%rbp  <- crashes here, probably fetching zend_string_hash_val(str) for an invalid str pointer
  474125:       48 85 ed                test   %rbp,%rbp
  474128:       74 7e                   je     4741a8 <zend_interned_string_find_permanent+0x98>
....

EDIT: I obtained a core dump. I was mistaken about what called zend_interned_string_find_permanent(). The source before signal_handler can vary (memcached, curl, reading files, etc), but it's just any point when signal_handler can get called for the httpd stop.

For gdb /path/to/libphp7.so path/to/core_dump

Program terminated with signal 11, Segmentation fault.                                                                         
...
(gdb) bt                                              
#0  0x00007f3e483ca121 in zend_interned_string_find_permanent () from /usr/local/php/modules/libphp7.so
#1  0x00007f3e3d0679f9 in accel_shutdown () from /usr/local/php/lib/php/20170718/opcache.so            
#2  0x00007f3e3d069ff0 in zm_shutdown_zend_accelerator () from /usr/local/php/lib/php/20170718/opcache.so
#3  0x00007f3e483a3ae3 in module_destructor () from /usr/local/php/modules/libphp7.so
#4  0x00007f3e4839b3cc in module_destructor_zval () from /usr/local/php/modules/libphp7.so             
#5  0x00007f3e483afa48 in zend_hash_graceful_reverse_destroy () from /usr/local/php/modules/libphp7.so
#6  0x00007f3e4839d1ce in zend_shutdown () from /usr/local/php/modules/libphp7.so                        
#7  0x00007f3e4832f99b in php_module_shutdown () from /usr/local/php/modules/libphp7.so
#8  0x00007f3e4832fa59 in php_module_shutdown_wrapper () from /usr/local/php/modules/libphp7.so
#9  0x00007f3e48466e51 in php_apache_child_shutdown () from /usr/local/php/modules/libphp7.so         
#10 0x00007f3e503011ae in apr_pool_destroy () from /lib64/libapr-1.so.0          
#11 0x00007f3e4ada823c in clean_child_exit () from /etc/httpd/modules/mod_mpm_prefork.so
#12 0x00007f3e4ada827b in just_die () from /etc/httpd/modules/mod_mpm_prefork.so               
#13 0x00007f3e483ca30d in zend_signal_handler () from /usr/local/php/modules/libphp7.so      
#14 0x00007f3e483ca45b in zend_signal_handler_defer () from /usr/local/php/modules/libphp7.so
#15 <signal handler called>                                                                                                    
#16 0x00007f3e500da6f0 in __read_nocancel () from /lib64/libpthread.so.0        
#17 0x00007f3e4834d079 in php_stdiop_read () from /usr/local/php/modules/libphp7.so    
#18 0x00007f3e4834770c in _php_stream_fill_read_buffer () from /usr/local/php/modules/libphp7.so
#19 0x00007f3e48347ba7 in _php_stream_get_line () from /usr/local/php/modules/libphp7.so
#20 0x00007f3e4829cb03 in php_exec () from /usr/local/php/modules/libphp7.so
#21 0x00007f3e4829ce7a in zif_exec () from /usr/local/php/modules/libphp7.so                                               
#22 0x00007f3e4845a8ec in execute_ex () from /usr/local/php/modules/libphp7.so         
#23 0x00007f3e48465664 in zend_execute () from /usr/local/php/modules/libphp7.so                                                                                                                                                                               
#24 0x00007f3e4839d830 in zend_execute_scripts () from /usr/local/php/modules/libphp7.so                                                                                                                                                                       
#25 0x00007f3e4832fcf0 in php_execute_script () from /usr/local/php/modules/libphp7.so                                                                                                                                                                         
#26 0x00007f3e484680ca in php_handler () from /usr/local/php/modules/libphp7.so                                                                                                                                                                                
#27 0x000055c9bc02ca40 in ?? ()                                                                                                                                                                                                                                
#28 0x000055c9bc75ca30 in ?? ()                                                                                                                                                                                                                                
#29 0x000055c9bc3f4be0 in ?? ()                                                                                                                                                                                                                                
#30 0x000055c9bc6e5ad0 in ?? ()                                                                                                
#31 0x000055c9bc02cf89 in ?? ()                                                                                                
#32 0x000055c9bc40bad8 in ?? ()                                                                                                
#33 0x000055c9bc025c4f in ?? ()                                                                                                
#34 0x000000005e0fbb63 in ?? ()                                                                                                
#35 0x951cbc1dbc51bb00 in ?? ()                                                                                                
#36 0x000055c9bc75dfc6 in ?? ()                                                                                                
#37 0x000055c9bc75ca30 in ?? ()                                                                                                
#38 0x0000000000000000 in ?? ()

EDIT: The larger problem is that this is a hard restart instead of a graceful restart, so the details of shutdown are less important.

phpv8 / v8js

Avoid uses of zend_string_dup/zend_string_copy when it will outlive the http request #432