glcpp: Avoid accidental token pasting in preprocessed result.

Consider this test case:

	#define EMPTY
	int foo = 1+EMPTY+4;

The expression should compile as the sequence of tokens 1, PLUS,
UNARY_POSITIVE, 4. But glcpp has been failing for this case since it
results in the string "1++4" which a compiler correctly sees as a
syntax error, (1, POST_INCREMENT, 4).

We fix this by changing any macro with an empty definition to result
in a single SPACE token rather than nothing. This then gives "1+ +4"
which compiles correctly.

This commit does touch up the two existing test cases which already
have empty macros, (to add the space to the expected result).

It also adds a new test case to exercise the above scenario.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/glsl/glcpp/tests/068-accidental-pasting.c.expected b/src/glsl/glcpp/tests/068-accidental-pasting.c.expected
new file mode 100644
index 00000000000..ce41cd6e524
--- /dev/null
+++ b/src/glsl/glcpp/tests/068-accidental-pasting.c.expected
@@ -0,0 +1,12 @@
+
+< <
+< =
+> >
+> =
+= =
+! =
+& &
+| |
++ +
+- -
+