One likely reason for the failure of fdopen() is a lack of free
memory.

Also expose a new function, fdopen_with_retry(), which retries on
ENOMEM but doesn't die() on errors. In a moment this function will be
used elsewhere.

Suggested-by: Jonathan Nieder <jrnie...@gmail.com>
Signed-off-by: Michael Haggerty <mhag...@alum.mit.edu>
---
 git-compat-util.h | 11 +++++++++++
 wrapper.c         | 28 +++++++++++++++++++++++++---
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index 3455c5e..a5652a7 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -672,7 +672,18 @@ extern ssize_t xread(int fd, void *buf, size_t len);
 extern ssize_t xwrite(int fd, const void *buf, size_t len);
 extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);
 extern int xdup(int fd);
+
+/*
+ * Like fdopen(), but if the first attempt fails with ENOMEM, try to
+ * free up some memory and try again.
+ */
+extern FILE *fdopen_with_retry(int fd, const char *mode);
+
+/*
+ * Like fdopen_with_retry(), but die on errors.
+ */
 extern FILE *xfdopen(int fd, const char *mode);
+
 extern int xmkstemp(char *template);
 extern int xmkstemp_mode(char *template, int mode);
 extern int odb_mkstemp(char *template, size_t limit, const char *pattern);
diff --git a/wrapper.c b/wrapper.c
index d5a6cef..b60cc03 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -311,14 +311,36 @@ int xdup(int fd)
        return ret;
 }
 
-FILE *xfdopen(int fd, const char *mode)
+FILE *fdopen_with_retry(int fd, const char *mode)
 {
        FILE *stream = fdopen(fd, mode);
-       if (stream == NULL)
-               die_errno("Out of memory? fdopen failed");
+
+       if (!stream && errno == ENOMEM) {
+               /*
+                * Try to free up some memory, then try again. We
+                * would prefer to use sizeof(FILE) here, but that is
+                * not guaranteed to be defined (e.g., FILE might be
+                * an incomplete type).
+                */
+               try_to_free_routine(1000);
+               stream = fdopen(fd, mode);
+       }
+
        return stream;
 }
 
+FILE *xfdopen(int fd, const char *mode)
+{
+       FILE *stream = fdopen_with_retry(fd, mode);
+
+       if (stream)
+               return stream;
+       else if (errno == ENOMEM)
+               die_errno("Out of memory? fdopen failed");
+       else
+               die_errno("fdopen failed");
+}
+
 int xmkstemp(char *template)
 {
        int fd;
-- 
2.1.4

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