[6 Regession] Usage of unitialized pointer io/list_read.c (

[Jerry DeLisle]

The title of the PR should be "Mishandling of namelist comments" or
"Interpreting '!' as a comment in non-namelist reads".

The attached patch fixes the regression by reverting the previous attempt at
namelist comments that used only CASE_SEPARATOR to enable comments in namelists.
 The approach now is to test specifically for '!' in each type of read various
functions. If in namelist mode the respective case falls through to the handling
of separators which eats the line when a '!' is found.  Otherwise, the read is
determined to be bad and an error is issued.

Since the reporter of this PR noticed something screwy with the 'new' pointer in
push_char4, I took a close look at the code and deleted it.  I also heavily
instrumented and tested this mechanism to grow the buffer and deleted the use of
memset which was commented to not be needed. The 'new' was not being initialized
and I think was a leftover from a previous edit and just missed.

I added two new test cases in the patch. These test all the new error
conditions. Also, read_bang4.f90 uses a large kind=4 string to exercise the
buffer mechanism. Verification is through making sure what we read in matches
what we wrote out to the test scratch file

Regression tested on x86_64-Linux.  OK for trunk? any thoughts on back porting
to 5 since it fixes a potentially bad pointer problem in push_char4?

Regards,

Jerry

2016-02-15  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

	PR libgfortran/69651
	* io/list_read.c: Entire file trailing spaces removed.
	(CASE_SEPARATORS): Remove '!'.
	(is_separator): Add namelist mode as condition with '!'.
	(push_char): Remove un-needed memset. (push_char4): Likewise and remove
	'new' pointer. (eat_separator): Remove un-needed use of notify_std.
	(read_logical): If '!' bang encountered when not in namelist mode got
	bad_logical to give an error. (read_integer): Likewise reject '!'.
	(read_character): Remove condition testing c = '!' which is now inside
	the is_separator macro. (parse_real): Reject '!' unless in namelist mode.
	(read_complex): Reject '!' unless in namelist mode. (read_real): Likewise
	reject '!'.
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