WIP #10
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WIP #10
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…ithm Right now the FNV-1 algorithm is used for determine the realpath cache key. For applications that are light-weight, but have lots of files (e.g. WordPress), the realpath cache key computation shows up in the Callgrind profile. The reason is that we do a simple byte-by-byte loop. Furthermore, we always use the 32-bit prime and offset values, even in a 64-bit environment which reduces the diffusion property of the hash. This hinders the distribution of keys a bit (although probably not a lot since we have only limited entries in the cache). I propose to switch to our regular string hashing algorithm, which is better optimised than a byte-per-byte loop, and has better diffusion on 64-bit systems. I don't know why FNV-1 was chosen over the DJB33X algorithm we use in the normal string hashing. Also, I don't know why FNV-1A wasn't chosen instead of FNV-1, which would be a simple modification and would distribute the hashes better than FNV-1. The only thing I can think of is that typically FNV-1A has a better distribution than DJB33X algorithms like what we use for string hashing [1]. But I doubt that makes a difference here, and if it does then we should perhaps look into changing the string hash algorithm from DJB33X to FNV-1A. [1] https://softwareengineering.stackexchange.com/questions/49550/which-hashing-algorithm-is-best-for-uniqueness-and-speed
nielsdos
pushed a commit
that referenced
this pull request
Oct 13, 2024
even without sanitizers, it is reproducible but with the following
```
<?php
$g = gmp_init(256);
var_dump(gmp_pow($g, PHP_INT_MAX));
```
we get this
```
AddressSanitizer:DEADLYSIGNAL
=================================================================
==286922==ERROR: AddressSanitizer: FPE on unknown address 0x03e8000460ca (pc 0x7faf6c69de5c bp 0x400000000000004 sp 0x7ffe9843c740 T0)
#0 0x7faf6c69de5c in __pthread_kill_implementation nptl/pthread_kill.c:44
#1 0x7faf6c649c81 in __GI_raise ../sysdeps/posix/raise.c:26
#2 0x7faf6db9386c in __gmp_exception (/lib/x86_64-linux-gnu/libgmp.so.10+0xd86c) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#3 0x7faf6db938d3 in __gmp_overflow_in_mpz (/lib/x86_64-linux-gnu/libgmp.so.10+0xd8d3) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#4 0x7faf6dbac95c in __gmpz_realloc (/lib/x86_64-linux-gnu/libgmp.so.10+0x2695c) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#5 0x7faf6dba9038 in __gmpz_n_pow_ui (/lib/x86_64-linux-gnu/libgmp.so.10+0x23038) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#6 0x5565ae1ccd9f in zif_gmp_pow /home/dcarlier/Contribs/php-src/ext/gmp/gmp.c:1286
#7 0x5565aee96ea9 in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:1312
#8 0x5565af144320 in execute_ex /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:56075
#9 0x5565af160f07 in zend_execute /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:60439
#10 0x5565aed6fafe in zend_execute_scripts /home/dcarlier/Contribs/php-src/Zend/zend.c:1842
#11 0x5565aeae70a8 in php_execute_script /home/dcarlier/Contribs/php-src/main/main.c:2578
#12 0x5565af532f4e in do_cli /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:964
#13 0x5565af535877 in main /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:1334
#14 0x7faf6c633d67 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
#15 0x7faf6c633e24 in __libc_start_main_impl ../csu/libc-start.c:360
#16 0x5565adc04040 in _start (/home/dcarlier/Contribs/php-src/sapi/cli/php+0x2604040) (BuildId: 949049955bdf8b7197390b1978a1dfc3ef6fdf38)
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: FPE nptl/pthread_kill.c:44 in __pthread_kill_implementation
==286922==ABORTING
```
nielsdos
pushed a commit
that referenced
this pull request
Oct 26, 2024
even without sanitizers, it is reproducible but with the following
```
<?php
$g = gmp_init(256);
var_dump(gmp_pow($g, PHP_INT_MAX));
```
we get this
```
AddressSanitizer:DEADLYSIGNAL
=================================================================
==286922==ERROR: AddressSanitizer: FPE on unknown address 0x03e8000460ca (pc 0x7faf6c69de5c bp 0x400000000000004 sp 0x7ffe9843c740 T0)
#0 0x7faf6c69de5c in __pthread_kill_implementation nptl/pthread_kill.c:44
#1 0x7faf6c649c81 in __GI_raise ../sysdeps/posix/raise.c:26
#2 0x7faf6db9386c in __gmp_exception (/lib/x86_64-linux-gnu/libgmp.so.10+0xd86c) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#3 0x7faf6db938d3 in __gmp_overflow_in_mpz (/lib/x86_64-linux-gnu/libgmp.so.10+0xd8d3) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#4 0x7faf6dbac95c in __gmpz_realloc (/lib/x86_64-linux-gnu/libgmp.so.10+0x2695c) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#5 0x7faf6dba9038 in __gmpz_n_pow_ui (/lib/x86_64-linux-gnu/libgmp.so.10+0x23038) (BuildId: 1af68a49fe041a5bb48a2915c3d47541f713bb38)
#6 0x5565ae1ccd9f in zif_gmp_pow /home/dcarlier/Contribs/php-src/ext/gmp/gmp.c:1286
#7 0x5565aee96ea9 in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:1312
#8 0x5565af144320 in execute_ex /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:56075
#9 0x5565af160f07 in zend_execute /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:60439
#10 0x5565aed6fafe in zend_execute_scripts /home/dcarlier/Contribs/php-src/Zend/zend.c:1842
#11 0x5565aeae70a8 in php_execute_script /home/dcarlier/Contribs/php-src/main/main.c:2578
#12 0x5565af532f4e in do_cli /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:964
#13 0x5565af535877 in main /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:1334
#14 0x7faf6c633d67 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
#15 0x7faf6c633e24 in __libc_start_main_impl ../csu/libc-start.c:360
#16 0x5565adc04040 in _start (/home/dcarlier/Contribs/php-src/sapi/cli/php+0x2604040) (BuildId: 949049955bdf8b7197390b1978a1dfc3ef6fdf38)
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: FPE nptl/pthread_kill.c:44 in __pthread_kill_implementation
==286922==ABORTING
```
close phpGH-16384
nielsdos
pushed a commit
that referenced
this pull request
Mar 29, 2025
```
ext/gd/libgd/gd.c:2275:14: runtime error: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
#0 0x5d6a2103e1db in php_gd_gdImageCopy /home/dcarlier/Contribs/php-src/ext/gd/libgd/gd.c:2275
#1 0x5d6a210a2b63 in gdImageCrop /home/dcarlier/Contribs/php-src/ext/gd/libgd/gd_crop.c:57
#2 0x5d6a21018ca4 in zif_imagecrop /home/dcarlier/Contribs/php-src/ext/gd/gd.c:3575
#3 0x5d6a21e46e7a in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:1337
#4 0x5d6a221188da in execute_ex /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:57246
#5 0x5d6a221366bd in zend_execute /home/dcarlier/Contribs/php-src/Zend/zend_vm_execute.h:61634
#6 0x5d6a21d107a6 in zend_execute_scripts /home/dcarlier/Contribs/php-src/Zend/zend.c:1895
#7 0x5d6a21a63409 in php_execute_script /home/dcarlier/Contribs/php-src/main/main.c:2529
#8 0x5d6a22516d5e in do_cli /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:966
#9 0x5d6a2251981d in main /home/dcarlier/Contribs/php-src/sapi/cli/php_cli.c:1341
#10 0x7f10d002a3b7 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
#11 0x7f10d002a47a in __libc_start_main_impl ../csu/libc-start.c:360
#12 0x5d6a20a06da4 in _start (/home/dcarlier/Contribs/php-src/sapi/cli/php+0x2806da4) (BuildId: d9a79c7e0e4872311439d7313cb3a81fe04190a2)
```
close phpGH-18006
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