Narrowing down preprocessor-related potential defect

[thutt@vmware.com]

Jonathan Wakely writes:
 > âs  External Email
 >
 > On Tue, 21 Jun 2022 at 20:31, thutt--- via Gcc <gcc@gcc.gnu.org> wrote:
 > >    I am here to solicit ideas on how to further narrow this this
 > >    down.  Is there any undocumented option that I can use to cause the
 > >    standalone preprocessor to produce output identical to input?
 > >    Note that '-traditional-cpp' does not work because some of the code
 > >    is not recognized (variadic macros, for example).
 >
 > This seems off-topic for the gcc mailing list. It belongs on the gcc-help list.
 >
 > Have you tried not using a standalone preprocessor?

 I am not using a standalone preprocessor.  Only using gcc directly to
 preprocess and compile the file results in the failure.

 > The usual approach is to add -save-temps to the gcc invocation, so it
 > leaves the preprocessed output in a separate .i file.

This doesn't have a satisfactory outcome.  The file is preprocessed
and multiple spaces appear to be replaced with a single space.  The
resultant output has no tabs that are not in quoted strings.  It is
currently believed the failure is produced when a mix of tabs and
spaces are present.

 >
 > N.B. it's a warning, not an error. You told GCC to turn that warning
 > into an error.

I'm aware of that.  We treat all warnings as errors.

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