Bug #77179 [NEW]: debug_backtrace() — Callstack arg values are modified inside the callee

From: signe at cothlamadh dot net Operating system: macOS 10.14.2 PHP version: 7.2.12 Package: Scripting Engine problem Bug Type: Bug Bug description:debug_backtrace() — Callstack arg values are modified inside the callee Description: ------------ If a function modifies one of its parameters internally (not via reference), the argument list returned by the backtrace functions reflects the modification not the initial value. The callstack arguments are being modified after the call is made. Interestingly, this doesn't seem to affect functions which are using their default parameters. Occurs in both debug_backtrace() and debug_print_backtrace() Test script calls a pair of recursing functions — in the first, a parameter is passed to the top-most function normally. In the second, the parameter's default value is used. Stack entry #10 is modified in the first case and not in the second. Test script: --------------- <?php echo "''\n"; foo(''); echo "\n\n"; echo "NULL\n"; foo(); function foo($str = '') { if (strlen($str) >= 30) { debug_print_backtrace(); return; } $str .= 'foo'; echo "'$str'\n"; bar($str); } function bar($str) { $str .= 'bar'; echo "'$str'\n";; foo($str); } Expected result: ---------------- '' 'foo' 'foobar' 'foobarfoo' 'foobarfoobar' 'foobarfoobarfoo' 'foobarfoobarfoobar' 'foobarfoobarfoobarfoo' 'foobarfoobarfoobarfoobar' 'foobarfoobarfoobarfoobarfoo' 'foobarfoobarfoobarfoobarfoobar' #0 foo(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26] #1 bar(foobarfoobarfoobarfoobarfoo) called at [/private/tmp/foo.php:19] #2 foo(foobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26] #3 bar(foobarfoobarfoobarfoo) called at [/private/tmp/foo.php:19] #4 foo(foobarfoobarfoobar) called at [/private/tmp/foo.php:26] #5 bar(foobarfoobarfoo) called at [/private/tmp/foo.php:19] #6 foo(foobarfoobar) called at [/private/tmp/foo.php:26] #7 bar(foobarfoo) called at [/private/tmp/foo.php:19] #8 foo(foobar) called at [/private/tmp/foo.php:26] #9 bar(foo) called at [/private/tmp/foo.php:19] #10 foo() called at [/private/tmp/foo.php:3] NULL 'foo' 'foobar' 'foobarfoo' 'foobarfoobar' 'foobarfoobarfoo' 'foobarfoobarfoobar' 'foobarfoobarfoobarfoo' 'foobarfoobarfoobarfoobar' 'foobarfoobarfoobarfoobarfoo' 'foobarfoobarfoobarfoobarfoobar' #0 foo(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26] #1 bar(foobarfoobarfoobarfoobarfoo) called at [/private/tmp/foo.php:19] #2 foo(foobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26] #3 bar(foobarfoobarfoobarfoo) called at [/private/tmp/foo.php:19] #4 foo(foobarfoobarfoobar) called at [/private/tmp/foo.php:26] #5 bar(foobarfoobarfoo) called at [/private/tmp/foo.php:19] #6 foo(foobarfoobar) called at [/private/tmp/foo.php:26] #7 bar(foobarfoo) called at [/private/tmp/foo.php:19] #8 foo(foobar) called at [/private/tmp/foo.php:26] #9 bar(foo) called at [/private/tmp/foo.php:38] #10 foo() called at [/private/tmp/foo.php:8] Actual result: -------------- '' 'foo' 'foobar' 'foobarfoo' 'foobarfoobar' 'foobarfoobarfoo' 'foobarfoobarfoobar' 'foobarfoobarfoobarfoo' 'foobarfoobarfoobarfoobar' 'foobarfoobarfoobarfoobarfoo' 'foobarfoobarfoobarfoobarfoobar' #0 foo(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26] #1 bar(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:19] #2 foo(foobarfoobarfoobarfoobarfoo) called at [/private/tmp/foo.php:26] #3 bar(foobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:19] #4 foo(foobarfoobarfoobarfoo) called at [/private/tmp/foo.php:26] #5 bar(foobarfoobarfoobar) called at [/private/tmp/foo.php:19] #6 foo(foobarfoobarfoo) called at [/private/tmp/foo.php:26] #7 bar(foobarfoobar) called at [/private/tmp/foo.php:19] #8 foo(foobarfoo) called at [/private/tmp/foo.php:26] #9 bar(foobar) called at [/private/tmp/foo.php:19] #10 foo(foo) called at [/private/tmp/foo.php:3] NULL 'foo' 'foobar' 'foobarfoo' 'foobarfoobar' 'foobarfoobarfoo' 'foobarfoobarfoobar' 'foobarfoobarfoobarfoo' 'foobarfoobarfoobarfoobar' 'foobarfoobarfoobarfoobarfoo' 'foobarfoobarfoobarfoobarfoobar' #0 foo(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26] #1 bar(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:19] #2 foo(foobarfoobarfoobarfoobarfoo) called at [/private/tmp/foo.php:26] #3 bar(foobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:19] #4 foo(foobarfoobarfoobarfoo) called at [/private/tmp/foo.php:26] #5 bar(foobarfoobarfoobar) called at [/private/tmp/foo.php:19] #6 foo(foobarfoobarfoo) called at [/private/tmp/foo.php:26] #7 bar(foobarfoobar) called at [/private/tmp/foo.php:19] #8 foo(foobarfoo) called at [/private/tmp/foo.php:26] #9 bar(foobar) called at [/private/tmp/foo.php:38] #10 foo() called at [/private/tmp/foo.php:8] -- Edit bug report at https://bugs.php.net/bug.php?id=77179&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=77179&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=77179&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=77179&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=77179&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=77179&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=77179&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=77179&r=needscript Try newer version: https://bugs.php.net/fix.php?id=77179&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=77179&r=support Expected behavior: https://bugs.php.net/fix.php?id=77179&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=77179&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=77179&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=77179&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=77179&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=77179&r=dst IIS Stability: https://bugs.php.net/fix.php?id=77179&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=77179&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=77179&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=77179&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=77179&r=mysqlcfg