From 83e4862a1d9a023f1c2a19a1938d761cb020d6d8 Mon Sep 17 00:00:00 2001
From: Maxime Devos <maximedevos@telenet.be>
Date: Wed, 10 Mar 2021 20:50:07 +0100
Subject: [PATCH 05/17] =?UTF-8?q?Define=20=E2=80=98symlinkat=E2=80=99=20wr?=
 =?UTF-8?q?apper=20when=20supported.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* configure.ac: Detect whether ‘symlinkat’ exists.
* libguile/filesys.c (scm_symlinkat): Define a Scheme binding
  when it exists.
* libguile/filesys.h: Make the binding part of the public C API.
* doc/ref/posix.texi (File System): Document the binding.
---
 configure.ac       |  2 +-
 doc/ref/posix.texi |  6 ++++++
 libguile/filesys.c | 23 +++++++++++++++++++++++
 libguile/filesys.h |  1 +
 4 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 551856fc4..1af02bb7b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -482,7 +482,7 @@ AC_CHECK_HEADERS([assert.h crt_externs.h])
 #
 AC_CHECK_FUNCS([DINFINITY DQNAN cexp chsize clog clog10 ctermid         \
   fesetround ftime ftruncate fchown fchmod fchdir readlinkat		\
-  getcwd geteuid getsid							\
+  symlinkat getcwd geteuid getsid							\
   gettimeofday getuid getgid gmtime_r ioctl lstat mkdir mkdtemp mknod   \
   nice readlink rename rmdir setegid seteuid                            \
   setlocale setuid setgid setpgid setsid sigaction siginterrupt stat64  \
diff --git a/doc/ref/posix.texi b/doc/ref/posix.texi
index 80ee02b93..eff49b5a5 100644
--- a/doc/ref/posix.texi
+++ b/doc/ref/posix.texi
@@ -919,6 +919,12 @@ Create a symbolic link named @var{newpath} with the value (i.e., pointing to)
 @var{oldpath}.  The return value is unspecified.
 @end deffn
 
+@deffn {Scheme Procedure} symlinkat dir oldpath newpath
+@deffnx {C Function} scm_symlinkat (dir, oldpath, newpath)
+Like @code{symlink}, but resolve @var{newpath} relative to
+the directory referred to by the file port @var{dir}.
+@end deffn
+
 @deffn {Scheme Procedure} mkdir path [mode]
 @deffnx {C Function} scm_mkdir (path, mode)
 Create a new directory named by @var{path}.  If @var{mode} is omitted
diff --git a/libguile/filesys.c b/libguile/filesys.c
index 06a550fc8..f86b5bb70 100644
--- a/libguile/filesys.c
+++ b/libguile/filesys.c
@@ -1081,6 +1081,29 @@ SCM_DEFINE (scm_symlink, "symlink", 2, 0, 0,
 #undef FUNC_NAME
 #endif /* HAVE_SYMLINK */
 
+#ifdef HAVE_SYMLINKAT
+SCM_DEFINE (scm_symlinkat, "symlinkat", 3, 0, 0,
+            (SCM dir, SCM oldpath, SCM newpath),
+            "Like @code{symlink}, but resolve @var{newpath} relative\n"
+            "to the directory referred to by the file port @var{dir}.")
+#define FUNC_NAME s_scm_symlinkat
+{
+  int val;
+  int fdes;
+
+  SCM_VALIDATE_OPFPORT (SCM_ARG1, dir);
+  fdes = SCM_FPORT_FDES (dir);
+  STRING2_SYSCALL (oldpath, c_oldpath,
+		   newpath, c_newpath,
+		   val = symlinkat (c_oldpath, fdes, c_newpath));
+  scm_remember_upto_here_1 (dir);
+  if (val != 0)
+    SCM_SYSERROR;
+  return SCM_UNSPECIFIED;
+}
+#undef FUNC_NAME
+#endif /* HAVE_SYMLINKAT */
+
 /* Static helper function for choosing between readlink
    and readlinkat. */
 static int
diff --git a/libguile/filesys.h b/libguile/filesys.h
index a3b257c12..d181aca52 100644
--- a/libguile/filesys.h
+++ b/libguile/filesys.h
@@ -62,6 +62,7 @@ SCM_API SCM scm_select (SCM reads, SCM writes, SCM excepts, SCM secs, SCM msecs)
 SCM_API SCM scm_fcntl (SCM object, SCM cmd, SCM value);
 SCM_API SCM scm_fsync (SCM object);
 SCM_API SCM scm_symlink (SCM oldpath, SCM newpath);
+SCM_API SCM scm_symlinkat (SCM dir, SCM oldpath, SCM newpath);
 SCM_API SCM scm_readlink (SCM path);
 SCM_API SCM scm_lstat (SCM str);
 SCM_API SCM scm_copy_file (SCM oldfile, SCM newfile);
-- 
2.30.2