bug#31817: Possible bug in regex search

["Michele Pes" <mp81ss@rambler.ru>]

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Hi,I'm working with regex, and I isolated an unexpected behaviour.If I paste
attached code code in scratch buffer and evaluate it, emacs hangs (cpu stays at
100% until I kill emacs)Im running emacs for windows x64, in particular this
package:
https://sourceforge.net/projects/emacsbinw64/files/release/emacs-w64-25.3-O2-with-modules.7z/download
The variable case-fold-search is set to t.
Can you help me?
Thank you very much,
Michele Pes

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(let (
      (regex
       (concat "[ \f\t\n\r\v]" "*\\(" "_*[[:alpha:]]+[A-Z0-9a-z_]*"
               "[ \f\t\n\r\v\\*]"
               "*\\)+(" "[ \f\t\n\r\v]"
               "*\\*" "[ \f\t\n\r\v]"
               "*\\(" "_*[[:alpha:]]+[A-Z0-9a-z_]*" "\\)"
               "[ \f\t\n\r\v]" "*[()]"))

      (x "void Vsdk_Init(void) {     /* Open watchdog iwdt driver, watchdog is running now */     iwdt.p_api->open"))
  (if (string-match "(" x)
      (prog2
          (string-match regex x)
          (match-string 2 x))
    (message "did not match")))