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+#!@BASH@
+# -*- mode: scheme; coding: utf-8; -*-
+
+# XXX: We have to go through Bash because there's no command-line switch to
+# augment %load-compiled-path, and because of the silly 127-byte limit for
+# the shebang line in Linux.
+# Use `load-compiled' because `load' (and `-l') doesn't otherwise load our
+# .go file (see <http://bugs.gnu.org/12519>).
+
+main="(@ (gnu build-support ld-wrapper) ld-wrapper)"
+exec @GUILE@ -c "(load-compiled \"@SELF@.go\") (apply $main (cdr (command-line)))" "$@"
+!#
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2012, 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (gnu build-support ld-wrapper)
+ #:use-module (srfi srfi-1)
+ #:use-module (ice-9 match)
+ #:export (ld-wrapper))
+
+;;; Commentary:
+;;;
+;;; This is a wrapper for the linker. Its purpose is to inspect the -L and
+;;; -l switches passed to the linker, add corresponding -rpath arguments, and
+;;; invoke the actual linker with this new set of arguments.
+;;;
+;;; The alternatives to this hack would be:
+;;;
+;;; 1. Using $LD_RUN_PATH. However, that would tend to include more than
+;;; needed in the RPATH; for instance, given a package with `libfoo' as
+;;; an input, all its binaries would have libfoo in their RPATH,
+;;; regardless of whether they actually NEED it.
+;;;
+;;; 2. Use a GCC "lib" spec string such as `%{L*:-rpath %*}', which adds a
+;;; `-rpath LIBDIR' argument for each occurrence of `-L LIBDIR'.
+;;; However, this doesn't work when $LIBRARY_PATH is used, because the
+;;; additional `-L' switches are not matched by the above rule, because
+;;; the rule only matches explicit user-provided switches. See
+;;; <http://gcc.gnu.org/ml/gcc-help/2012-09/msg00110.html> for details.
+;;;
+;;; As a bonus, this wrapper checks for "impurities"--i.e., references to
+;;; libraries outside the store.
+;;;
+;;; Code:
+
+(define %real-ld
+ ;; Name of the linker that we wrap.
+ "@LD@")
+
+(define %store-directory
+ ;; File name of the store.
+ (or (getenv "NIX_STORE") "/gnu/store"))
+
+(define %temporary-directory
+ ;; Temporary directory.
+ (or (getenv "TMPDIR") "/tmp"))
+
+(define %build-directory
+ ;; Top build directory when run from a builder.
+ (getenv "NIX_BUILD_TOP"))
+
+(define %allow-impurities?
+ ;; Whether to allow references to libraries outside the store.
+ (getenv "GUIX_LD_WRAPPER_ALLOW_IMPURITIES"))
+
+(define %debug?
+ ;; Whether to emit debugging output.
+ (getenv "GUIX_LD_WRAPPER_DEBUG"))
+
+(define %disable-rpath?
+ ;; Whether to disable automatic '-rpath' addition.
+ (getenv "GUIX_LD_WRAPPER_DISABLE_RPATH"))
+
+(define (readlink* file)
+ ;; Call 'readlink' until the result is not a symlink.
+ (define %max-symlink-depth 50)
+
+ (let loop ((file file)
+ (depth 0))
+ (define (absolute target)
+ (if (absolute-file-name? target)
+ target
+ (string-append (dirname file) "/" target)))
+
+ (if (>= depth %max-symlink-depth)
+ file
+ (call-with-values
+ (lambda ()
+ (catch 'system-error
+ (lambda ()
+ (values #t (readlink file)))
+ (lambda args
+ (let ((errno (system-error-errno args)))
+ (if (or (= errno EINVAL) (= errno ENOENT))
+ (values #f file)
+ (apply throw args))))))
+ (lambda (success? target)
+ (if success?
+ (loop (absolute target) (+ depth 1))
+ file))))))
+
+(define (pure-file-name? file)
+ ;; Return #t when FILE is the name of a file either within the store
+ ;; (possibly via a symlink) or within the build directory.
+ (let ((file (readlink* file)))
+ (or (not (string-prefix? "/" file))
+ (string-prefix? %store-directory file)
+ (string-prefix? %temporary-directory file)
+ (and %build-directory
+ (string-prefix? %build-directory file)))))
+
+(define (store-file-name? file)
+ ;; Return #t when FILE is a store file, possibly indirectly.
+ (string-prefix? %store-directory (readlink* file)))
+
+(define (shared-library? file)
+ ;; Return #t when FILE denotes a shared library.
+ (or (string-suffix? ".so" file)
+ (let ((index (string-contains file ".so.")))
+ ;; Since we cannot use regexps during bootstrap, roll our own.
+ (and index
+ (string-every (char-set-union (char-set #\.) char-set:digit)
+ (string-drop file (+ index 3)))))))
+
+(define (library-files-linked args)
+ ;; Return the file names of shared libraries explicitly linked against via
+ ;; `-l' or with an absolute file name in ARGS.
+ (define path+files+args
+ (fold (lambda (argument result)
+ (match result
+ ((library-path library-files ("-dynamic-linker" . rest))
+ ;; When passed '-dynamic-linker ld.so', ignore 'ld.so'.
+ ;; See <http://bugs.gnu.org/20102>.
+ (list library-path
+ library-files
+ (cons* argument "-dynamic-linker" rest)))
+ ((library-path library-files previous-args)
+ (cond ((string-prefix? "-L" argument) ;augment the search path
+ (list (append library-path
+ (list (string-drop argument 2)))
+ library-files
+ (cons argument previous-args)))
+ ((string-prefix? "-l" argument) ;add library
+ (let* ((lib (string-append "lib"
+ (string-drop argument 2)
+ ".so"))
+ (full (search-path library-path lib)))
+ (list library-path
+ (if full
+ (cons full library-files)
+ library-files)
+ (cons argument previous-args))))
+ ((and (string-prefix? %store-directory argument)
+ (shared-library? argument)) ;add library
+ (list library-path
+ (cons argument library-files)
+ (cons argument previous-args)))
+ (else
+ (list library-path
+ library-files
+ (cons argument previous-args)))))))
+ (list '() '() '())
+ args))
+
+ (match path+files+args
+ ((path files arguments)
+ (reverse files))))
+
+(define (rpath-arguments library-files)
+ ;; Return the `-rpath' argument list for each of LIBRARY-FILES, a list of
+ ;; absolute file names.
+ (fold-right (lambda (file args)
+ ;; Add '-rpath' if and only if FILE is in the store; we don't
+ ;; want to add '-rpath' for files under %BUILD-DIRECTORY or
+ ;; %TEMPORARY-DIRECTORY because that could leak to installed
+ ;; files.
+ (cond ((and (not %disable-rpath?)
+ (store-file-name? file))
+ (cons* "-rpath" (dirname file) args))
+ ((or %allow-impurities?
+ (pure-file-name? file))
+ args)
+ (else
+ (begin
+ (format (current-error-port)
+ "ld-wrapper: error: attempt to use \
+impure library ~s~%"
+ file)
+ (exit 1)))))
+ '()
+ library-files))
+
+(define (ld-wrapper . args)
+ ;; Invoke the real `ld' with ARGS, augmented with `-rpath' switches.
+ (let* ((libs (library-files-linked args))
+ (args (append args (rpath-arguments libs))))
+ (when %debug?
+ (format (current-error-port)
+ "ld-wrapper: libraries linked: ~s~%" libs)
+ (format (current-error-port)
+ "ld-wrapper: invoking `~a' with ~s~%"
+ %real-ld args))
+ (apply execl %real-ld (basename %real-ld) args)))
+
+;;; ld-wrapper.scm ends here