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* [musl] [PATCH] __stdio_write: retry on interrupted system call
@ 2021-05-15  1:37 Dominic Chen
  2021-05-15 15:00 ` Rich Felker
  0 siblings, 1 reply; 2+ messages in thread
From: Dominic Chen @ 2021-05-15  1:37 UTC (permalink / raw)
  To: musl

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I've noticed that my C++ application stops printing to stdout after a 
while, and I didn't know why. It turns out that printing via 
'std::ostream::operator<<' will eventually call '__stdio_write()', which 
then calls 'writev()'. But, if 'writev()' is interrupted by a signal and 
SA_RESTART is not set, then it will return EINTR, which will cause both 
the 'FILE' structure and the corresponding C++ stream to be marked bad. 
I think the current behavior is very confusing, so attached is a patch 
to retry on EINTR.

Thanks,

Dominic


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From 6428a3baaf65b26d7b2c4e09d1688a0cb08fa4f7 Mon Sep 17 00:00:00 2001
From: Dominic Chen <d.c.ddcc@gmail.com>
Date: Fri, 14 May 2021 21:09:33 -0400
Subject: [PATCH] __stdio_write: retry on interrupted system call

---
 src/stdio/__stdio_write.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/stdio/__stdio_write.c b/src/stdio/__stdio_write.c
index d2d89475..142af0bf 100644
--- a/src/stdio/__stdio_write.c
+++ b/src/stdio/__stdio_write.c
@@ -19,6 +19,8 @@ size_t __stdio_write(FILE *f, const unsigned char *buf, size_t len)
 			return len;
 		}
 		if (cnt < 0) {
+			if (errno == EINTR)
+				continue;
 			f->wpos = f->wbase = f->wend = 0;
 			f->flags |= F_ERR;
 			return iovcnt == 2 ? 0 : len-iov[0].iov_len;
-- 
2.25.1


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2021-05-15  1:37 [musl] [PATCH] __stdio_write: retry on interrupted system call Dominic Chen
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