[PATCH v3] cmd: Fix copying when the dest is one of the sources.

[Lauri Kenttä]

"COPY a+b a" appends b to a.
"COPY a+b b" skips b from the sources.
(Previously Wine just fails.)

Fixes the main issue of bug 35495.

v2: Detect same file properly with GetFileInformationByHandle
instead of simply comparing paths.

v3: Check handles against INVALID_HANDLE_VALUE, not zero.
Signed-off-by: Lauri Kenttä <lauri.kentta at gmail.com>
---
 programs/cmd/builtins.c                  | 44 ++++++++++++++++++++++++++++++--
 programs/cmd/tests/test_builtins.cmd     | 16 ++++++++++++
 programs/cmd/tests/test_builtins.cmd.exp |  3 +++
 3 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/programs/cmd/builtins.c b/programs/cmd/builtins.c
index a29a502..95a9dc7 100644
--- a/programs/cmd/builtins.c
+++ b/programs/cmd/builtins.c
@@ -460,6 +460,36 @@ static BOOL WCMD_AppendEOF(WCHAR *filename)
 }
 
 /****************************************************************************
+ * WCMD_IsSameFile
+ *
+ * Checks if the two paths reference to the same file
+ */
+static BOOL WCMD_IsSameFile(const WCHAR *name1, const WCHAR *name2)
+{
+  BOOL ret = FALSE;
+  HANDLE file1 = INVALID_HANDLE_VALUE, file2 = INVALID_HANDLE_VALUE;
+  BY_HANDLE_FILE_INFORMATION info1, info2;
+
+  file1 = CreateFileW(name1, 0, FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_EXISTING, 0, 0);
+  if (file1 == INVALID_HANDLE_VALUE || !GetFileInformationByHandle(file1, &info1))
+    goto end;
+
+  file2 = CreateFileW(name2, 0, FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_EXISTING, 0, 0);
+  if (file2 == INVALID_HANDLE_VALUE || !GetFileInformationByHandle(file2, &info2))
+    goto end;
+
+  ret = info1.dwVolumeSerialNumber == info2.dwVolumeSerialNumber
+    && info1.nFileIndexHigh == info2.nFileIndexHigh
+    && info1.nFileIndexLow == info2.nFileIndexLow;
+end:
+  if (file1 != INVALID_HANDLE_VALUE)
+    CloseHandle(file1);
+  if (file2 != INVALID_HANDLE_VALUE)
+    CloseHandle(file2);
+  return ret;
+}
+
+/****************************************************************************
  * WCMD_ManualCopy
  *
  * Copies from a file
@@ -922,6 +952,7 @@ void WCMD_copy(WCHAR * args) {
       do {
         WCHAR outname[MAX_PATH];
         BOOL  overwrite;
+        BOOL  appendtofirstfile = FALSE;
 
         /* Skip . and .., and directories */
         if (!srcisdevice && fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
@@ -946,8 +977,14 @@ void WCMD_copy(WCHAR * args) {
           WINE_TRACE("Flags: srcbinary(%d), dstbinary(%d), over(%d), prompt(%d)\n",
                      thiscopy->binarycopy, destination->binarycopy, overwrite, prompt);
 
+          if (!writtenoneconcat) {
+            appendtofirstfile = anyconcats && WCMD_IsSameFile(srcpath, outname);
+          }
+
           /* Prompt before overwriting */
-          if (!overwrite) {
+          if (appendtofirstfile) {
+            overwrite = TRUE;
+          } else if (!overwrite) {
             DWORD attributes = GetFileAttributesW(outname);
             if (attributes != INVALID_FILE_ATTRIBUTES) {
               WCHAR* question;
@@ -969,7 +1006,10 @@ void WCMD_copy(WCHAR * args) {
 
           /* Do the copy as appropriate */
           if (overwrite) {
-            if (anyconcats && writtenoneconcat) {
+            if (anyconcats && WCMD_IsSameFile(srcpath, outname)) {
+              /* Silently skip if the destination file is also a source file */
+              status = TRUE;
+            } else if (anyconcats && writtenoneconcat) {
               if (thiscopy->binarycopy) {
                 status = WCMD_ManualCopy(srcpath, outname, FALSE, TRUE);
               } else {
diff --git a/programs/cmd/tests/test_builtins.cmd b/programs/cmd/tests/test_builtins.cmd
index b49f90a..02d9750 100644
--- a/programs/cmd/tests/test_builtins.cmd
+++ b/programs/cmd/tests/test_builtins.cmd
@@ -2584,6 +2584,22 @@ rem Concat 2 files, default mode - (one EOF on the end 5+8+1)
 copy ..\file1+..\file2 file12_eof2 >nul 2>&1
 call :CheckFileSize file12_eof2 14
 
+rem Test copying when destination is one of the sources.
+rem Concat file1+file2+file3 into file1, should produce file1+file2+file3 = 24
+copy /y ..\file? .\ >nul 2>&1
+copy /y /b file1+file2+file3 file1 >nul 2>&1
+call :CheckFileSize file1 24
+
+rem Concat file1+file2+file3 into file2, should produce file1+file3 = 16
+copy /y ..\file? .\ >nul 2>&1
+copy /y /b file1+file2+file3 file2 >nul 2>&1
+call :CheckFileSize file2 16
+
+rem Concat file1+file2+file3 into file3, should produce file1+file2 = 13
+copy /y ..\file? .\ >nul 2>&1
+copy /y /b file1+file2+file3 file3 >nul 2>&1
+call :CheckFileSize file3 13
+
 rem --------------------------------------------------------------
 rem Show ascii source copy stops at first EOF, binary does the lot
 rem --------------------------------------------------------------
diff --git a/programs/cmd/tests/test_builtins.cmd.exp b/programs/cmd/tests/test_builtins.cmd.exp
index e81fbcb..796550e 100644
--- a/programs/cmd/tests/test_builtins.cmd.exp
+++ b/programs/cmd/tests/test_builtins.cmd.exp
@@ -1462,6 +1462,9 @@ Passed: file size check on file3_plus_eof [12]@or_broken at Skipping file size chec
 Passed: file size check on file12_plus_eof [14]@or_broken at Skipping file size check on NT4
 Passed: file size check on file12_no_eof [13]@or_broken at Skipping file size check on NT4
 Passed: file size check on file12_eof2 [14]@or_broken at Skipping file size check on NT4
+Passed: file size check on file1 [24]@or_broken at Skipping file size check on NT4
+Passed: file size check on file2 [16]@or_broken at Skipping file size check on NT4
+Passed: file size check on file3 [13]@or_broken at Skipping file size check on NT4
 Passed: file size check on file1_binary_srccopy [6]@or_broken at Skipping file size check on NT4
 Passed: file size check on file1_ascii_srccopy [5]@or_broken at Skipping file size check on NT4
 Passed: file size check on file123_default_copy [25]@or_broken at Skipping file size check on NT4
-- 
2.10.2