On Tue, Sep 19, 2023 at 06:08:50PM +0100, Richard Sandiford wrote:
> Lewis Hyatt via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> > Hello-
> >
> > This fixes an old PR, bootstrap + regtest on x86-64 Linux. Please let me
> > know if it's ok? Thanks!
> >
> > -Lewis
> >
> > -- >8 --
> >
> > As noted in the PR, GCC will segfault if a file name is first seen in a
> > linemarker directive, and then later seen in a normal #include. This is
> > because the fake include process adds the file to the cache with a null PATH
> > member. The normal #include finds this file in the cache and then attempts
> > to use the null PATH. Resolve by adding the file to the cache with a unique
> > starting directory, so that the fake entry will only be found by a
> > subsequent fake include, not by a real one.
> >
> > libcpp/ChangeLog:
> >
> > PR preprocessor/61474
> > * files.cc (_cpp_find_file): Set DONT_READ to TRUE for fake
> > include files.
> > (_cpp_fake_include): Pass a unique cpp_dir* address so
> > the fake file will not be found when looked up for real.
> >
> > gcc/testsuite/ChangeLog:
> >
> > PR preprocessor/61474
> > * c-c++-common/cpp/pr61474-2.h: New test.
> > * c-c++-common/cpp/pr61474.c: New test.
> > * c-c++-common/cpp/pr61474.h: New test.
>
> Neat fix! I don't know this code very well, but I agree it looks
> correct. OK if no-one objects in 24 hours.
Looks fine to me too, thanks Lewis.
> Thanks,
> Richard
>
> > ---
> > libcpp/files.cc | 11 +++++++++--
> > gcc/testsuite/c-c++-common/cpp/pr61474-2.h | 1 +
> > gcc/testsuite/c-c++-common/cpp/pr61474.c | 5 +++++
> > gcc/testsuite/c-c++-common/cpp/pr61474.h | 6 ++++++
> > 4 files changed, 21 insertions(+), 2 deletions(-)
> > create mode 100644 gcc/testsuite/c-c++-common/cpp/pr61474-2.h
> > create mode 100644 gcc/testsuite/c-c++-common/cpp/pr61474.c
> > create mode 100644 gcc/testsuite/c-c++-common/cpp/pr61474.h
> >
> > diff --git a/libcpp/files.cc b/libcpp/files.cc
> > index 43a8894b7de..27301d79fa4 100644
> > --- a/libcpp/files.cc
> > +++ b/libcpp/files.cc
> > @@ -541,7 +541,9 @@ _cpp_find_file (cpp_reader *pfile, const char *fname,
> > cpp_dir *start_dir,
> > = (kind == _cpp_FFK_PRE_INCLUDE
> > || (pfile->buffer && pfile->buffer->file->implicit_preinclude));
> >
> > - if (kind != _cpp_FFK_FAKE)
> > + if (kind == _cpp_FFK_FAKE)
> > + file->dont_read = true;
> > + else
> > /* Try each path in the include chain. */
> > for (;;)
> > {
> > @@ -1490,7 +1492,12 @@ cpp_clear_file_cache (cpp_reader *pfile)
> > void
> > _cpp_fake_include (cpp_reader *pfile, const char *fname)
> > {
> > - _cpp_find_file (pfile, fname, pfile->buffer->file->dir, 0,
> > _cpp_FFK_FAKE, 0);
> > + /* It does not matter what are the contents of fake_source_dir, it will
> > never
> > + be inspected; we just use its address to uniquely signify that this
> > file
> > + was added as a fake include, so a later call to _cpp_find_file (to
> > include
> > + the file for real) won't find the fake one in the hash table. */
> > + static cpp_dir fake_source_dir;
> > + _cpp_find_file (pfile, fname, &fake_source_dir, 0, _cpp_FFK_FAKE, 0);
> > }
> >
> > /* Not everyone who wants to set system-header-ness on a buffer can
> > diff --git a/gcc/testsuite/c-c++-common/cpp/pr61474-2.h
> > b/gcc/testsuite/c-c++-common/cpp/pr61474-2.h
> > new file mode 100644
> > index 00000000000..6f70f09beec
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/cpp/pr61474-2.h
> > @@ -0,0 +1 @@
> > +#pragma once
> > diff --git a/gcc/testsuite/c-c++-common/cpp/pr61474.c
> > b/gcc/testsuite/c-c++-common/cpp/pr61474.c
> > new file mode 100644
> > index 00000000000..f835a40fc7a
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/cpp/pr61474.c
> > @@ -0,0 +1,5 @@
> > +/* { dg-do preprocess } */
> > +#include "pr61474.h"
> > +/* Make sure that the file can be included for real, after it was
> > + fake-included by the linemarker directives in pr61474.h. */
> > +#include "pr61474-2.h"
> > diff --git a/gcc/testsuite/c-c++-common/cpp/pr61474.h
> > b/gcc/testsuite/c-c++-common/cpp/pr61474.h
> > new file mode 100644
> > index 00000000000..d9e8c3a1fec
> > --- /dev/null
> > +++ b/gcc/testsuite/c-c++-common/cpp/pr61474.h
> > @@ -0,0 +1,6 @@
> > +/* Create a fake include for pr61474-2.h and exercise looking it up. */
> > +/* Use #pragma once to check also that the fake-include entry in the file
> > + cache does not cause a problem in
> > libcpp/files.cc:has_unique_contents(). */
> > +#pragma once
> > +# 1 "pr61474-2.h" 1
> > +# 2 "pr61474-2.h" 1
>
Marek
