shell32/tests: CommandLineToArgvW("") shouldn't truncate returned exe path

[Ilya Basin]

This exposes http://bugs.winehq.org/show_bug.cgi?id=21758
Currently CommandLineToArgvW("") returns only the first 6 characters
of the exe path. And even worse, it doesn't terminate the result
string with 0, which can potentially cause access violations.

Here's the crosstest output:
[il at IL wine-git]$ ./wine dlls/shell32/tests/shell32_crosstest.exe shlexec
...
shlexec.c:2182: Test failed: wrong path to the current executable
  expected: L"Z:\\home\\il\\builds\\wine-git\\dlls\\shell32\\tests\\shell32_crosstest.exe"
  got     : L"Z:\\homCe\64d0\0013("
shlexec: 411 tests executed (0 marked as todo, 21 failures), 0 skipped.

---
 dlls/shell32/tests/shlexec.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/dlls/shell32/tests/shlexec.c b/dlls/shell32/tests/shlexec.c
index b883d0b..7d1cb03 100644
--- a/dlls/shell32/tests/shlexec.c
+++ b/dlls/shell32/tests/shlexec.c
@@ -2118,8 +2118,9 @@ static void test_commandline(void)
     static const WCHAR chkfmt3[] = {'\\','\"','%','s','\"',0};
     static const WCHAR chkfmt4[] = {'%','s','=','%','s','\"',' ','%','s','\"',0};
     WCHAR cmdline[255];
-    LPWSTR *args = (LPWSTR*)0xdeadcafe;
+    LPWSTR *args = (LPWSTR*)0xdeadcafe, pbuf;
     INT numargs = -1;
+    size_t bufsize, buflen;
 
     wsprintfW(cmdline,fmt1,one,two,three,four);
     args=CommandLineToArgvW(cmdline,&numargs);
@@ -2170,6 +2171,19 @@ static void test_commandline(void)
     wsprintfW(cmdline,fmt6);
     args=CommandLineToArgvW(cmdline,&numargs);
     ok(numargs == 1, "expected 1 args, got %i\n",numargs);
+    if (numargs >= 1) {
+        buflen = max(lstrlenW(args[0])+1,256);
+        bufsize = buflen*sizeof(pbuf[0]);
+        pbuf = HeapAlloc(GetProcessHeap(), 0, bufsize);
+        GetModuleFileNameW(NULL, pbuf, buflen);
+        pbuf[buflen-1] = 0;
+        /* check module file name starts with args[0] */
+        /* wine's CommandLineToArgvW may return broken string, so use wine_dbgstr_w() */
+        todo_wine ok(lstrcmpW(args[0],pbuf)==0,
+            "wrong path to the current executable\n  expected: %s\n  got     : %s\n", 
+            wine_dbgstr_w(pbuf), wine_dbgstr_w(args[0]));
+        HeapFree(GetProcessHeap(), 0, pbuf);
+    }
 }
 
 START_TEST(shlexec)
-- 
1.7.1