CPreProcessor: (bugfix) don't return negative value other than EOF from unget-buffer

Fix #4222

When putting a char getting from the unget-buffer to a vstring,
returning a nagative value caused a crash.

This change focuses on values returned from
ungetBufferGetcFromUngetBuffer, a function for getting from the
unget-buffer.

I will revise the functions putting values to the
unget-buffer in the later commits.

Signed-off-by: Masatake YAMATO <[email protected]>

Author: masatake

Units/parser-cpreprocessor.r/unget-mbyte-string.d/README

@@ -0,0 +1 @@
+This is a crash test.

Units/parser-cpreprocessor.r/unget-mbyte-string.d/input-0.lds

@@ -0,0 +1 @@
+i"犬"

Units/parser-cpreprocessor.r/unget-mbyte-string.d/input-1.java

@@ -0,0 +1 @@
+a(i'犬'

Units/parser-cpreprocessor.r/unget-mbyte-string.d/input-2.lds

@@ -0,0 +1 @@
+i'犬'

Units/parser-cpreprocessor.r/unget-mbyte-string.d/input.java

@@ -0,0 +1 @@
+a(i"犬"

Units/parser-cpreprocessor.r/unget-multi-bytes-string.d/README

@@ -0,0 +1 @@
+This is a crash test.

Units/parser-cpreprocessor.r/unget-multi-bytes-string.d/input-0.lds

@@ -0,0 +1 @@
+i"犬"

Units/parser-cpreprocessor.r/unget-multi-bytes-string.d/input-1.java

@@ -0,0 +1 @@
+a(i'犬'

Units/parser-cpreprocessor.r/unget-multi-bytes-string.d/input-2.lds

@@ -0,0 +1 @@
+i'犬'

Units/parser-cpreprocessor.r/unget-multi-bytes-string.d/input.java

@@ -0,0 +1 @@
+a(i"犬"

parsers/cpreprocessor.c

@@ -652,7 +652,7 @@ static int ungetBufferGetcFromUngetBuffer (ungetBuffer *ungetBuffer)
 		Assert(ungetBuffer->size > 0);
 		Assert(ungetBuffer->dataSize > 0);
 
-		int c = *(ungetBuffer->pointer);
+		unsigned char c = *(ungetBuffer->pointer);
 		ungetBuffer->dataSize--;
 		if(ungetBuffer->dataSize > 0)
 			ungetBuffer->pointer++;