Description:
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In release build, it triggers an segfault:
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MemorySanitizer:DEADLYSIGNAL
==160146==ERROR: MemorySanitizer: SEGV on unknown address 0x000000000018 (pc 0x000000f8da84 bp 0x000000000000 sp 0x7ffe10b2de00 T160146)
==160146==The signal is caused by a READ memory access.
==160146==Hint: address points to the zero page.
    #0 0xf8da83 in php_str_replace_common /home/yongheng/php_clean/ext/standard/string.c:4379:3
    #1 0x1573b32 in ZEND_DO_ICALL_SPEC_RETVAL_UNUSED_HANDLER /home/yongheng/php_clean/Zend/zend_vm_execute.h:1236:2
    #2 0x13ec04f in execute_ex /home/yongheng/php_clean/Zend/zend_vm_execute.h:51852:7
    #3 0x13ec844 in zend_execute /home/yongheng/php_clean/Zend/zend_vm_execute.h:56146:2
    #4 0x1337c58 in zend_execute_scripts /home/yongheng/php_clean/Zend/zend.c:1667:4
    #5 0x10c1cd7 in php_execute_script /home/yongheng/php_clean/main/main.c:2579:14
    #6 0x171abf1 in do_cli /home/yongheng/php_clean/sapi/cli/php_cli.c:958:5
    #7 0x1716fcf in main /home/yongheng/php_clean/sapi/cli/php_cli.c:1357:18
    #8 0x7f78981f4b96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310
    #9 0x440309 in _start (/home/yongheng/php_clean/asan/sapi/cli/php+0x440309)

MemorySanitizer can not provide additional info.
SUMMARY: MemorySanitizer: SEGV /home/yongheng/php_clean/ext/standard/string.c:4379:3 in php_str_replace_common
==160146==ABORTING
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In debug build, it triggers an assertion:
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/home/yongheng/php_clean/ext/standard/string.c:4379: void php_str_replace_common(zend_execute_data *, zval *, int): Assertion `(zval_get_type(&(*(zcount))) == 10)' failed.
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Test script:
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<?
str_replace ( array () , 1.500000 , array () , DEFINED ( 678.000000 ) ) ;