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Date: Wed, 16 Jul 2025 22:45:32 +0900
To: cygwin AT cygwin DOT com
Subject: Re: doxygen hangs when many call graphs are generated.
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From: Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
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On Wed, 16 Jul 2025 21:36:04 +0900
Takashi Yano via Cygwin <cygwin AT cygwin DOT com> wrote:
> On Wed, 16 Jul 2025 21:13:59 +0900
> Takashi Yano via Cygwin <cygwin AT cygwin DOT com> wrote:
> 
> > On Tue, 17 Jun 2025 21:46:47 +0900
> > Takashi Yano wrote:
> > > I encountered a problem of doxygen when many call graphs are generated.
> > > 
> > > How to reproduce:
> > > 1) Make a empty directory.
> > > 2) Place two files (Doxyfile, x.c) attached in the directory.
> > > 3) Run doxygen in the directory.
> > > 
> > > It seems that this is a bug of cygwin1.dll and the cause is
> > > a deadlock in newlib/libc/stdio/findfp.c:__fp_lock_all().

A simple reproducer is as follows.

#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#include <sys/wait.h>

void *func(void *arg)
{
	while (1) {
		FILE *f = fopen("/usr/bin/cygwin1.dll", "r"); /* Open something */
		fclose(f);
	}
	return NULL;
}

int main()
{
	pthread_t th;
	pthread_create(&th, NULL, func, NULL);
	int cnt = 0;
	while (1) {
		if (fork() == 0) {
			return 0;
		} else {
			wait(NULL);
			printf("Done %d\n", cnt++);
		}
	}
}



-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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