From 0f9c90e0edd27d2db04d48e7bd98bb46d2c4a918 Mon Sep 17 00:00:00 2001
From: Matt Widmann <mw@mattwidmann.net>
Date: Sat, 25 Nov 2017 13:59:07 -0800
Subject: io: retry fgets on EINTR (#7632)

The calls to `fgets` in `src/nvim/if_cscope.c` (and elsewhere) can show
communication errors to the user if a signal is delivered during its
system calls. For plugins that proxy subprocess output into cscope
requests, a `SIGCHLD` might *always* interfere with calls into `fgets`.

To see this in a debugger, put a breakpoint on `cs_reading_emsg` and
watch signals come in (with lldb, using `process handle --notify true
--pass true`).  Next, run a subcommand from neovim that calls through
cscope when it returns.  A tag picker plugin, like vim-picker and fzy,
with `cscopetag` and `cscopetagorder=0` set, reproduced this reliably.
The breakpoint will hit after a `SIGCHLD` is delivered, and `errno` will
be set to 4, `EINTR`.

The caller of `fgets` should retry when `NULL` is returned with `errno`
set to `EINTR`.
---
 src/nvim/fileio.c | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'src/nvim/fileio.c')

diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index ae6c3f96e3..9214e1e644 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -4448,7 +4448,12 @@ bool vim_fgets(char_u *buf, int size, FILE *fp) FUNC_ATTR_NONNULL_ALL
   char tbuf[FGETS_SIZE];
 
   buf[size - 2] = NUL;
+retry:
+  errno = 0;
   eof = fgets((char *)buf, size, fp);
+  if (eof == NULL && errno == EINTR) {
+    goto retry;
+  }
   if (buf[size - 2] != NUL && buf[size - 2] != '\n') {
     buf[size - 1] = NUL;            /* Truncate the line */
 
-- 
cgit 


From bab2f8200aea09ad32bbcb2e83404bbd4076a227 Mon Sep 17 00:00:00 2001
From: Matt Widmann <mw@mattwidmann.net>
Date: Sat, 25 Nov 2017 13:27:59 -0800
Subject: io: fix handling EOF in vim_fgets

If an EOF is returned from `fgets`, `vim_fgets` might spin forever, as
it tries to consume the current line.

A `NULL` return value from `fgets` should break out of the function
(unless `errno` is `EINTR`), and then `feof` should be used to check for
the EOF condition on the stream.
---
 src/nvim/fileio.c | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

(limited to 'src/nvim/fileio.c')

diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 9214e1e644..1f4cd22754 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -4443,27 +4443,32 @@ char *modname(const char *fname, const char *ext, bool prepend_dot)
 /// @return true for end-of-file.
 bool vim_fgets(char_u *buf, int size, FILE *fp) FUNC_ATTR_NONNULL_ALL
 {
-  char        *eof;
-#define FGETS_SIZE 200
-  char tbuf[FGETS_SIZE];
+  char *retval;
 
+  assert(size > 0);
   buf[size - 2] = NUL;
-retry:
-  errno = 0;
-  eof = fgets((char *)buf, size, fp);
-  if (eof == NULL && errno == EINTR) {
-    goto retry;
-  }
+
+  do {
+    errno = 0;
+    retval = fgets((char *)buf, size, fp);
+  } while (retval == NULL && errno == EINTR);
+
   if (buf[size - 2] != NUL && buf[size - 2] != '\n') {
-    buf[size - 1] = NUL;            /* Truncate the line */
+    char tbuf[200];
+
+    buf[size - 1] = NUL;  // Truncate the line.
 
-    /* Now throw away the rest of the line: */
+    // Now throw away the rest of the line:
     do {
-      tbuf[FGETS_SIZE - 2] = NUL;
-      ignoredp = fgets((char *)tbuf, FGETS_SIZE, fp);
-    } while (tbuf[FGETS_SIZE - 2] != NUL && tbuf[FGETS_SIZE - 2] != '\n');
+      tbuf[sizeof(tbuf) - 2] = NUL;
+      errno = 0;
+      retval = fgets((char *)tbuf, sizeof(tbuf), fp);
+      if (retval == NULL && errno != EINTR) {
+        break;
+      }
+    } while (tbuf[sizeof(tbuf) - 2] != NUL && tbuf[sizeof(tbuf) - 2] != '\n');
   }
-  return eof == NULL;
+  return retval ? false : feof(fp);
 }
 
 /// Read 2 bytes from "fd" and turn them into an int, MSB first.
-- 
cgit