Skip testing argv[0] on target argv[0] isn't available

I see the following two fails on arm-none-eabi target, because argv[0]
isn't available.

print argv[0]^M
$1 = 0x1f78 "/dev/null"^M
(gdb) FAIL: gdb.base/argv0-symlink.exp: kept file symbolic link name

print argv[0]^M
$1 = 0x1f78 "/dev/null"^M
(gdb) FAIL: gdb.base/argv0-symlink.exp: kept directory symbolic link name

My first thought is to check [target_info exists noargs], and skip the
test if it returns true.  However, noargs is set in gdbserver board
files, so argv0-symlink.exp will be skipped on gdbserver board file.
The change is too aggressive.

When the program is running with gdbserver, argv[1] to argv[N] aren't
available, but argv[0] is.  Fortunately, argv0-symlink.exp only
requires argv[0].  argv0-symlink.exp can be run with gdbserver board
file, as what we do now.

What we need to check is whether argv[0] is available, so I add a new
proc gdb_has_argv0 to do so by starting a program, and check
argc/argv[0] to see whether argv[0] is available.

Dan fixed the similar problem by checking noargs, which is too strong.
https://sourceware.org/ml/gdb-patches/2010-02/msg00398.html as a
result, the test is skipped on gdbserver.  This patch fixed it too.

gdb/testsuite:

2014-10-18  Yao Qi  <yao@codesourcery.com>

	* gdb.base/argv0-symlink.exp: Check argv[0] value if
	gdb_has_argv0 return true.
	* gdb.guile/scm-value.exp (test_value_in_inferior): Don't
	check [target_info exists noargs], check [gdb_has_argv0]
	instead.
	* gdb.python/py-value.exp (test_value_in_inferior): Likewise.
	* lib/gdb.exp (gdb_has_argv0, gdb_has_argv0_1): New
	procedures.

gdb/testsuite/ChangeLog

@@ -1,3 +1,14 @@
+2014-10-18  Yao Qi  <yao@codesourcery.com>
+
+	* gdb.base/argv0-symlink.exp: Check argv[0] value if
+	gdb_has_argv0 return true.
+	* gdb.guile/scm-value.exp (test_value_in_inferior): Don't
+	check [target_info exists noargs], check [gdb_has_argv0]
+	instead.
+	* gdb.python/py-value.exp (test_value_in_inferior): Likewise.
+	* lib/gdb.exp (gdb_has_argv0, gdb_has_argv0_1): New
+	procedures.
+
 2014-10-17  Doug Evans  <dje@google.com>
 
 	* gdb.python/py-events.exp: Update expected output for clear_objfiles

gdb/testsuite/gdb.base/argv0-symlink.exp

@@ -15,6 +15,8 @@
 
 standard_testfile
 
+set has_argv0 [gdb_has_argv0]
+
 if { [build_executable ${testfile}.exp ${testfile} ${srcfile}] == -1 } {
     return -1
 }
@@ -39,7 +41,11 @@ if ![runto_main] {
 gdb_test_no_output "set print repeats 10000"
 gdb_test_no_output "set print elements 10000"
 
-gdb_test {print argv[0]} "/$filelink\"" $test
+if { $has_argv0 } {
+    gdb_test {print argv[0]} "/$filelink\"" $test
+} else {
+    unsupported $test
+}
 
 # For a link named /PATH/TO/DIR/LINK, we want to check the output
 # against "/DIR/LINK", but computed in a way that doesn't make
@@ -73,9 +79,14 @@ if ![runto_main] {
 gdb_test_no_output "set print repeats 10000"
 gdb_test_no_output "set print elements 10000"
 
-# gdbserver does not have this issue.
-if ![is_remote target] {
-    setup_kfail "*-*-*" gdb/15934
+if { $has_argv0 } {
+    # gdbserver does not have this issue.
+    if ![is_remote target] {
+	setup_kfail "*-*-*" gdb/15934
+    }
+    gdb_test {print argv[0]} "/$dirlink/$filelink\"" $test
+} else {
+    unsupported $test
 }
-gdb_test {print argv[0]} "/$dirlink/$filelink\"" $test
+
 gdb_test "info inferiors" "/$lastdir/$filelink *" "$test for info inferiors"

gdb/testsuite/gdb.guile/scm-value.exp

@@ -20,6 +20,8 @@ load_lib gdb-guile.exp
 
 standard_testfile
 
+set has_argv0 [gdb_has_argv0]
+
 # Build inferior to language specification.
 # LANG is one of "c" or "c++".
 proc build_inferior {exefile lang} {
@@ -86,9 +88,12 @@ proc test_value_in_inferior {} {
 	"set arg0"
 
     # Check that the dereferenced value is sane.
-    if { ! [target_info exists noargs] } {
-	gdb_test "gu (print arg0)" \
-	    "0x.*$testfile\"" "verify dereferenced value"
+    global has_argv0
+    set test "verify dereferenced value"
+    if { $has_argv0 } {
+	gdb_test "gu (print arg0)" "0x.*$testfile\"" $test
+    } else {
+	unsupported $test
     }
 
     # Smoke-test value-optimized-out?.

gdb/testsuite/gdb.python/py-value.exp

@@ -20,6 +20,8 @@ load_lib gdb-python.exp
 
 standard_testfile
 
+set has_argv0 [gdb_has_argv0]
+
 # Build inferior to language specification.
 # LANG is one of "c" or "c++".
 proc build_inferior {exefile lang} {
@@ -221,8 +223,12 @@ proc test_value_in_inferior {} {
   gdb_py_test_silent_cmd "python arg0 = argv.dereference ()" "dereference value" 1
 
   # Check that the dereferenced value is sane
-  if { ! [target_info exists noargs] } {
-    gdb_test "python print (arg0)" "0x.*$testfile\"" "verify dereferenced value"
+  global has_argv0
+  set test "verify dereferenced value"
+  if { $has_argv0 } {
+    gdb_test "python print (arg0)" "0x.*$testfile\"" $test
+  } else {
+    unsupported $test
   }
 
   # Smoke-test is_optimized_out attribute

gdb/testsuite/lib/gdb.exp

@@ -4216,6 +4216,104 @@ gdb_caching_proc gdb_skip_xml_test {
     return $xml_missing
 }
 
+# Return true if argv[0] is available.
+
+gdb_caching_proc gdb_has_argv0 {
+    set result 0
+
+    # Set up, compile, and execute a test program to check whether
+    # argv[0] is available.
+    set src [standard_temp_file has_argv0[pid].c]
+    set exe [standard_temp_file has_argv0[pid].x]
+
+    gdb_produce_source $src {
+	int main (int argc, char **argv) {
+	    return 0;
+	}
+    }
+
+    gdb_compile $src $exe executable {debug}
+
+    # Helper proc.
+    proc gdb_has_argv0_1 { exe } {
+	global srcdir subdir
+	global gdb_prompt hex
+
+	gdb_exit
+	gdb_start
+	gdb_reinitialize_dir $srcdir/$subdir
+	gdb_load "$exe"
+
+	# Set breakpoint on main.
+	gdb_test_multiple "break main" "break main" {
+	    -re "Breakpoint.*${gdb_prompt} $" {
+	    }
+	    -re "${gdb_prompt} $" {
+		return 0
+	    }
+	}
+
+	# Run to main.
+	gdb_run_cmd
+	gdb_test_multiple "" "run to main" {
+	    -re "Breakpoint.*${gdb_prompt} $" {
+	    }
+	    -re "${gdb_prompt} $" {
+		return 0
+	    }
+	}
+
+	# Check whether argc is 1.
+	gdb_test_multiple "p argc" "p argc" {
+	    -re " = 1\r\n${gdb_prompt} $" {
+
+		gdb_test_multiple "p argv\[0\]" "p argv\[0\]" {
+		    -re " = $hex \".*[file tail $exe]\"\r\n${gdb_prompt} $" {
+			return 1
+		    }
+		    -re "${gdb_prompt} $" {
+			return 0
+		    }
+		}
+	    }
+	    -re "${gdb_prompt} $" {
+		return 0
+	    }
+	}
+	return 0
+    }
+
+    set result [gdb_has_argv0_1 $exe]
+
+    gdb_exit
+    file delete $src
+    file delete $exe
+
+    if { !$result
+      && ([istarget *-*-linux*]
+	  || [istarget *-*-freebsd*] || [istarget *-*-kfreebsd*]
+	  || [istarget *-*-netbsd*] || [istarget *-*-knetbsd*]
+	  || [istarget *-*-openbsd*]
+	  || [istarget *-*-darwin*]
+	  || [istarget *-*-solaris*]
+	  || [istarget *-*-aix*]
+	  || [istarget *-*-gnu*]
+	  || [istarget *-*-cygwin*] || [istarget *-*-mingw32*]
+	  || [istarget *-*-*djgpp*] || [istarget *-*-go32*]
+	  || [istarget *-wince-pe] || [istarget *-*-mingw32ce*]
+	  || [istarget *-*-symbianelf*]
+	  || [istarget *-*-osf*]
+	  || [istarget *-*-hpux*]
+	  || [istarget *-*-dicos*]
+	  || [istarget *-*-nto*]
+	  || [istarget *-*-*vms*]
+	  || [istarget *-*-lynx*178]) } {
+	fail "argv\[0\] should be available on this target"
+    }
+
+    return $result
+}
+
 # Note: the procedure gdb_gnu_strip_debug will produce an executable called
 # ${binfile}.dbglnk, which is just like the executable ($binfile) but without
 # the debuginfo. Instead $binfile has a .gnu_debuglink section which contains