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# -*- 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 <>).
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 <>
;;; 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
;;; 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 <>.
(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
;;; <> 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.
(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.
(define %debug?
;; Whether to emit debugging output.
(define %disable-rpath?
;; Whether to disable automatic '-rpath' addition.
(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)
(string-append (dirname file) "/" target)))
(if (>= depth %max-symlink-depth)
(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))
(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', ignore ''.
;; See <>.
(list library-path
(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)))
(cons argument previous-args)))
((string-prefix? "-l" argument) ;add library
(let* ((lib (string-append "lib"
(string-drop argument 2)
(full (search-path library-path lib)))
(list library-path
(if full
(cons full 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)))
(list library-path
(cons argument previous-args)))))))
(list '() '() '())
(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))
(format (current-error-port)
"ld-wrapper: error: attempt to use \
impure library ~s~%"
(exit 1)))))
(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