[RFC PATCH 1/1] patch: Fix to error out for invalid patch

[Athira Rajeev]

When given an invalid patch, busybox reports zero exit code even if the patch is not applied.
With GNU patch, the behaviour is:

# patch < test.patch 
patch: **** Only garbage was found in the patch input.

With busybox patch, I get the following output:

busybox patch < test.patch 
[root at localhost ~]# echo $?
0

Input patch file contents:
==================

cat test.patch:

-- test.c.org	2015-07-15 11:27:51.100000000 +0000
++ test.c	2015-07-15 11:28:11.189000000 +0000
@@ -1,8 +1,8 @@
 #include <stdio.h>
 int main()
 {
-	int i;
-	for (int j ; j <10; j++)
+	int i,j;
+	for (j ; j <10; j++)
 	{
 		printf("j is %d\n", j);
 	}


and test.c file contents:

# cat test.c 
#include <stdio.h>
int main()
{
	int i;
	for (int j ; j <10; j++)
	{
		printf("j is %d\n", j);
	}

}


busybox code loops through patchlines and check for +++, switches state when patches found. 

// state 0: Not in a hunk, look for +++.
// state 1: Found +++ file indicator, look for @@
// state 2: In hunk: counting initial context lines
// state 3: In hunk: getting body

state 2 implies code is getting into the hunk. 
Loop exits if patchline is empty

Adding a patch which has following changes:

- When state is 2, set patch_found to true ( implies a valid patch exists )
- when patchline is NULL,  ( i.e. when end of patch is reached ), set exitval to 1 if:
		patchfile size is non-zero ( that means some content is there in the patch file ) 
		and patch_found is false ( that means no valid patches were found )

Signed-off-by: Athira Rajeev<atrajeev at linux.vnet.ibm.com>


diff --git a/editors/patch.c b/editors/patch.c
index 988021d..6bfdf19 100644
--- a/editors/patch.c
+++ b/editors/patch.c
@@ -352,11 +352,13 @@ int patch_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int patch_main(int argc UNUSED_PARAM, char **argv)
 {
 	int opts;
-	int reverse, state = 0;
+	int reverse, size, state = 0;
+	bool patch_found = false;
 	char *oldname = NULL, *newname = NULL;
 	char *opt_p, *opt_i;
 	long oldlen = oldlen; /* for compiler */
 	long newlen = newlen; /* for compiler */
+	struct stat buf;
 
 	INIT_TT();
 
@@ -373,12 +375,22 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
 		}
 	}
 
+	// Get the file size using fstat
+	fstat(STDIN_FILENO, &buf);
+	size = buf.st_size;
+
 	// Loop through the lines in the patch
 	for(;;) {
 		char *patchline;
 
 		patchline = xmalloc_fgetline(stdin);
-		if (!patchline) break;
+		if (!patchline) {
+			if (size !=0 && !patch_found) {
+				printf("Couldnt find a valid patch. \n");
+				TT.exitval = 1;
+			}
+			break;
+		}	
 
 		// Other versions of patch accept damaged patches,
 		// so we need to also.
@@ -460,6 +472,9 @@ int patch_main(int argc UNUSED_PARAM, char **argv)
 			TT.context = 0;
 			state = 2;
 
+			// In hunk, found unified diff, set patch_found
+			patch_found = true;
+
 			// If the --- line is missing or malformed, either oldname
 			// or (for -R) newname could be NULL -- but not both.  Like
 			// GNU patch, proceed based on the +++ line, and avoid SEGVs.




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