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authorJeff King <peff@peff.net>2017-06-14 05:30:18 (GMT)
committerJunio C Hamano <gitster@pobox.com>2017-06-15 21:14:33 (GMT)
commit3adf9fdecfb0cd31a83ef3af1d8d631a1acd392b (patch)
treea75b2e3f909a2aafbcc4b050bc153e79417a1d77
parente5b313442ab7c700d0851e9dbe7d2b029e3893e5 (diff)
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configure.ac: loosen FREAD_READS_DIRECTORIES test program
We added an FREAD_READS_DIRECTORIES Makefile knob long ago in cba22528f (Add compat/fopen.c which returns NULL on attempt to open directory, 2008-02-08) to handle systems where reading from a directory returned garbage. This works by catching the problem at the fopen() stage and returning NULL. More recently, we found that there is a class of systems (including Linux) where fopen() succeeds but fread() fails. Since the solution is the same (having fopen return NULL), they use the same Makefile knob as of e2d90fd1c (config.mak.uname: set FREAD_READS_DIRECTORIES for Linux and FreeBSD, 2017-05-03). This works fine except for one thing: the autoconf test in configure.ac to set FREAD_READS_DIRECTORIES actually checks whether fread succeeds. Which means that on Linux systems, the knob isn't set (and we even override the config.mak.uname default). t1308 catches the failure. We can fix this by tweaking the autoconf test to cover both cases. In theory we might care about the distinction between the traditional "fread reads directories" case and the new "fopen opens directories". But since our solution catches the problem at the fopen stage either way, we don't actually need to know the difference. The "fopen" case is a superset. This does mean the FREAD_READS_DIRECTORIES name is slightly misleading. Probably FOPEN_OPENS_DIRECTORIES would be more accurate. But it would be disruptive to simply change the name (people's existing build configs would fail), and it's not worth the complexity of handling both. Let's just add a comment in the knob description. Reported-by: √ėyvind A. Holm <sunny@sunbase.org> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--Makefile3
-rw-r--r--configure.ac4
2 files changed, 4 insertions, 3 deletions
diff --git a/Makefile b/Makefile
index e35542e..4307588 100644
--- a/Makefile
+++ b/Makefile
@@ -19,7 +19,8 @@ all::
# have been written to the final string if enough space had been available.
#
# Define FREAD_READS_DIRECTORIES if you are on a system which succeeds
-# when attempting to read from an fopen'ed directory.
+# when attempting to read from an fopen'ed directory (or even to fopen
+# it at all).
#
# Define NO_OPENSSL environment variable if you do not have OpenSSL.
# This also implies BLK_SHA1.
diff --git a/configure.ac b/configure.ac
index 1281655..ceeb9de 100644
--- a/configure.ac
+++ b/configure.ac
@@ -865,9 +865,9 @@ AC_CACHE_CHECK([whether system succeeds to read fopen'ed directory],
[
AC_RUN_IFELSE(
[AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
- [[char c;
+ [[
FILE *f = fopen(".", "r");
- return f && fread(&c, 1, 1, f)]])],
+ return f)]])],
[ac_cv_fread_reads_directories=no],
[ac_cv_fread_reads_directories=yes])
])