tests: Skip tests that would fail due to the shebang length.

Reported by Daniel Kochmański <dkochmanski@hellsgate.pl>.
Fixes <http://bugs.gnu.org/19888>.

* guix/tests.scm (shebang-too-long?): New procedure.
* tests/builders.scm ("gnu-build"): Conditionalize on
  not (shebang-too-long?).
* tests/packages.scm ("GNU Make, bootstrap"): Likewise.
* tests/guix-package.sh (shebang_not_too_long): New function.
  Use it to determine whether to build 'gnu-make-boot0'.

guix/tests.scm

@@ -32,6 +32,7 @@
             random-text
             random-bytevector
             network-reachable?
+            shebang-too-long?
             mock
             %substitute-directory
             with-derivation-narinfo
@@ -185,6 +186,17 @@ CONTENTS."
       (delete-file (string-append dir "/example.out"))
       (delete-file (string-append dir "/example.nar")))))
 
+(define (shebang-too-long?)
+  "Return true if the typical shebang in the current store would exceed
+Linux's static limit---the BINPRM_BUF_SIZE constant, normally 128 characters
+all included."
+  (define shebang
+    (string-append "#!" (%store-prefix) "/"
+                   (make-string 32 #\a)
+                   "-bootstrap-binaries-0/bin/bash\0"))
+
+  (> (string-length shebang) 128))
+
 (define-syntax with-derivation-substitute
   (syntax-rules (sha256 =>)
     "Evaluate BODY in a context where DRV is substitutable with the given

tests/builders.scm

@@ -94,7 +94,8 @@
 (test-assert "gnu-build-system"
   (build-system? gnu-build-system))
 
-(unless (network-reachable?) (test-skip 1))
+(when (or (not (network-reachable?)) (shebang-too-long?))
+  (test-skip 1))
 (test-assert "gnu-build"
   (let* ((url      "http://ftp.gnu.org/gnu/hello/hello-2.8.tar.gz")
          (hash     (nix-base32-string->bytevector

tests/guix-package.sh

@@ -28,6 +28,14 @@ readlink_base ()
     basename `readlink "$1"`
 }
 
+# Return true if a typical shebang in the store would not exceed Linux's
+# default static limit.
+shebang_not_too_long ()
+{
+    test `echo $NIX_STORE_DIR/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-bootstrap-binaries-0/bin/bash | wc -c` \
+	 -lt 128
+}
+
 module_dir="t-guix-package-$$"
 profile="t-profile-$$"
 rm -f "$profile"
@@ -55,8 +63,9 @@ test -f "$profile/bin/guile"
 guix package --search-paths -p "$profile"
 test "`guix package --search-paths -p "$profile" | wc -l`" = 0
 
-# Check whether we have network access.
-if guile -c '(getaddrinfo "www.gnu.org" "80" AI_NUMERICSERV)' 2> /dev/null
+# Check whether we have network access and an acceptable shebang length.
+if guile -c '(getaddrinfo "www.gnu.org" "80" AI_NUMERICSERV)' 2> /dev/null \
+	 && shebang_not_too_long
 then
     boot_make="(@@ (gnu packages commencement) gnu-make-boot0)"
     boot_make_drv="`guix build -e "$boot_make" | grep -v -e -debug`"

tests/packages.scm

@@ -531,7 +531,8 @@
                      (%current-target-system "foo64-linux-gnu"))
         (equal? drv (bag->derivation %store bag))))))
 
-(unless (network-reachable?) (test-skip 1))
+(when (or (not (network-reachable?)) (shebang-too-long?))
+  (test-skip 1))
 (test-assert "GNU Make, bootstrap"
   ;; GNU Make is the first program built during bootstrap; we choose it
   ;; here so that the test doesn't last for too long.