See <http://lists.gnu.org/archive/html/bug-patch/2015-06/msg00009.html>

From 0507dfad5f060161f01840067e1bb1615257b636 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludovic=20Court=C3=A8s?= <ludo@gnu.org>
Date: Mon, 8 Jun 2015 17:27:56 +0200
Subject: [PATCH] Do not rely on PATH_MAX when reading a symlink target.

* src/util.c (move_file, copy_file): Use 'fromst->st_size + 1' and
'tost->st_size + 1' for the allocation, and 'fromst->st_size' and
'tost->st_size' instead of PATH_MAX.  Fixes compilation on GNU/Hurd.
---
 src/util.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/util.c b/src/util.c
index 1cc08ba..67dbd3a 100644
--- a/src/util.c
+++ b/src/util.c
@@ -460,12 +460,12 @@ move_file (char const *from, bool *from_needs_removal,
 
 	  /* FROM contains the contents of the symlink we have patched; need
 	     to convert that back into a symlink. */
-	  char *buffer = xmalloc (PATH_MAX);
+	  char *buffer = xmalloc (fromst->st_size + 1);
 	  int fd, size = 0, i;
 
 	  if ((fd = safe_open (from, O_RDONLY | O_BINARY, 0)) < 0)
 	    pfatal ("Can't reopen file %s", quotearg (from));
-	  while ((i = read (fd, buffer + size, PATH_MAX - size)) > 0)
+	  while ((i = read (fd, buffer + size, fromst->st_size - size)) > 0)
 	    size += i;
 	  if (i != 0 || close (fd) != 0)
 	    read_fatal ();
@@ -610,10 +610,10 @@ copy_file (char const *from, char const *to, struct stat *tost,
 
   if (S_ISLNK (mode))
     {
-      char *buffer = xmalloc (PATH_MAX + 1);
+      char *buffer = xmalloc (tost->st_size + 1);
       ssize_t r;
 
-      if ((r = safe_readlink (from, buffer, PATH_MAX)) < 0)
+      if ((r = safe_readlink (from, buffer, tost->st_size)) < 0)
 	pfatal ("Can't read %s %s", "symbolic link", from);
       buffer[r] = '\0';
       if (safe_symlink (buffer, to) != 0)
-- 
2.16.2

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<div class='path'>path: <a href='/guix/log/?id=5a1b2467361edcf8f2f9c7399658b4e136e979d4'>root</a>/<a href='/guix/log/tests?id=5a1b2467361edcf8f2f9c7399658b4e136e979d4'>tests</a>/<a href='/guix/log/tests/git.scm?id=5a1b2467361edcf8f2f9c7399658b4e136e979d4'>git.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/git.scm?id=5a1b2467361edcf8f2f9c7399658b4e136e979d4&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-10-17 09:37:27 +0200'>2022-10-17</span></td><td><a href='/guix/commit/tests/git.scm?id=46f7011591601b4783b2dc2c7252c41564ca0140'>git: 'update-cached-checkout' returns the commit ID when given a tag.</a><span class='msg-avail'>...<span class='msg-tooltip'>Previously, starting with commit
efa578ecaece67366b4b0e2266de7c2faaa4ae54, 'update-cached-checkout' would
return the OID of the annotated tag the tag points to.  With this change
it returns the OID of the commit object in all cases.

* guix/git.scm (resolve-reference): In the 'tag' case, call
'tag-target-id' and 'tag-lookup' when OID designates an annotated tag.
* tests/git.scm ("update-cached-checkout, tag"): New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-02-14 11:23:07 +0100'>2022-02-14</span></td><td><a href='/guix/commit/tests/git.scm?id=87d49346f3072f7b4343b6fb387ee5f9311493b7'>git: Add 'commit-descendant?'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/git.scm (commit-descendant?): New procedure.
* tests/git.scm ("commit-descendant?"): New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-09-18 19:37:45 +0200'>2021-09-18</span></td><td><a href='/guix/commit/tests/git.scm?id=59ee10754eddddb99e4a80b9e18aa12ed1b3d77a'>import: Add 'generic-git' updater.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/git.scm (ls-remote-refs): New procedure.
* tests/git.scm ("remote-refs" "remote-refs: only tags"): New tests.
* guix/import/git.scm: New file.
* doc/guix.texi (Invoking guix refresh): Document it.
* tests/import-git.scm: New test file.
* Makefile.am (MODULES, SCM_TESTS): Register the new files.

Co-authored-by: Sarah Morgensen &lt;iskarian@mgsn.dev&gt;
Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Xinglu Chen</td></tr>
<tr><td><span title='2020-06-09 00:34:52 +0200'>2020-06-09</span></td><td><a href='/guix/commit/tests/git.scm?id=72357e2170e88f73c11ff089f87a744cee8606ec'>git: 'commit-difference' really excludes the ancestors of #:excluded.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/git.scm (commit-difference): Initialize VISITED to the closure of
OLD and EXCLUDED, as written in the docstring.
* tests/git.scm ("commit-difference, excluded commits"): Adjust
accordingly.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-25 00:00:28 +0200'>2020-05-25</span></td><td><a href='/guix/commit/tests/git.scm?id=c098c11be8eb9e0c12be42640721e3cb21c37628'>git: Add 'commit-relation'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/git.scm (commit-relation): New procedure.
* tests/git.scm ("commit-relation"): New test.
</span></span></td><td>Ludovic Courtès</td></tr>