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From: Nathan Sidwell <nathan@acm.org>
To: "Torbjörn SVENSSON" <torbjorn.svensson@foss.st.com>,
	gcc-patches@gcc.gnu.org
Cc: yvan.roux@foss.st.com
Subject: Re: [PATCH] c++: Allow module name to be a single letter on Windows
Date: Thu, 3 Nov 2022 10:17:33 -0400	[thread overview]
Message-ID: <6c6abd06-ae1a-059b-a376-db738af5506e@acm.org> (raw)
In-Reply-To: <20221028091500.2748920-1-torbjorn.svensson@foss.st.com>

On 10/28/22 05:15, Torbjörn SVENSSON wrote:
> On Windows, the ':' character is special and when the module name is
> a single character, like 'A', then the flatname would be (for
> example) 'A:Foo'. On Windows, 'A:Foo' is treated as an absolute
> path by the module loader and is likely not found.
> 
> Without this patch, the test case pr98944_c.C fails with:
> 
> In module imported at /src/gcc/testsuite/g++.dg/modules/pr98944_b.C:7:1,
> of module A:Foo, imported at /src/gcc/testsuite/g++.dg/modules/pr98944_c.C:7:
> A:Internals: error: header module expected, module 'A:Internals' found
> A:Internals: error: failed to read compiled module: Bad file data
> A:Internals: note: compiled module file is 'gcm.cache/A-Internals.gcm'
> In module imported at /src/gcc/testsuite/g++.dg/modules/pr98944_c.C:7:8:
> A:Foo: error: failed to read compiled module: Bad import dependency
> A:Foo: note: compiled module file is 'gcm.cache/A-Foo.gcm'
> A:Foo: fatal error: returning to the gate for a mechanical issue
> compilation terminated.
> 
> include/ChangeLog:
> 
> 	* filenames.h: Added IS_REAL_ABSOLUTE_PATH macro to check if
> 	path is absolute and not semi-absolute on Windows.

Hm, this is unfortunate.  The current IS_ABSOLUTE_PATH, is really 'not relative 
to cwd', and even then that's untrue if the drive letter there is the drive 
letter of cwd, right?

It's awkward to have a new macro for just this purpose and the new name isn't 
very indicative of the difference to the current IS_ABSOLUTE_PATH.

Would it be better to not deal with drive letters here?  How prevalent are they 
these days in windows?  Would something like

    if (IS_DIR_SEPARATOR (ptr[ptr[0] == '.'])

suffice?

or, failing that perhaps put some explicit WINDOWS-specific #ifdef'd code there? 
  It's a real corner case.

nathan

> 
> gcc/cp/ChangeLog:
> 
> 	* module.cc: Use IS_REAL_ABSOLUTE_PATH macro.
> 
> Co-Authored-By: Yvan ROUX <yvan.roux@foss.st.com>
> Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
> ---
>   gcc/cp/module.cc    | 2 +-
>   include/filenames.h | 4 ++++
>   2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 9957df510e6..84680e183b7 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -13958,7 +13958,7 @@ get_module (tree name, module_state *parent, bool partition)
>   static module_state *
>   get_module (const char *ptr)
>   {
> -  if (ptr[0] == '.' ? IS_DIR_SEPARATOR (ptr[1]) : IS_ABSOLUTE_PATH (ptr))
> +  if (ptr[0] == '.' ? IS_DIR_SEPARATOR (ptr[1]) : IS_REAL_ABSOLUTE_PATH (ptr))
>       /* A header name.  */
>       return get_module (build_string (strlen (ptr), ptr));
>   
> diff --git a/include/filenames.h b/include/filenames.h
> index 6c72c422edd..d04fccfed64 100644
> --- a/include/filenames.h
> +++ b/include/filenames.h
> @@ -43,6 +43,7 @@ extern "C" {
>   #  define HAS_DRIVE_SPEC(f) HAS_DOS_DRIVE_SPEC (f)
>   #  define IS_DIR_SEPARATOR(c) IS_DOS_DIR_SEPARATOR (c)
>   #  define IS_ABSOLUTE_PATH(f) IS_DOS_ABSOLUTE_PATH (f)
> +#  define IS_REAL_ABSOLUTE_PATH(f) IS_DOS_REAL_ABSOLUTE_PATH (f)
>   #else /* not DOSish */
>   #  if defined(__APPLE__)
>   #    ifndef HAVE_CASE_INSENSITIVE_FILE_SYSTEM
> @@ -52,6 +53,7 @@ extern "C" {
>   #  define HAS_DRIVE_SPEC(f) (0)
>   #  define IS_DIR_SEPARATOR(c) IS_UNIX_DIR_SEPARATOR (c)
>   #  define IS_ABSOLUTE_PATH(f) IS_UNIX_ABSOLUTE_PATH (f)
> +#  define IS_REAL_ABSOLUTE_PATH(f) IS_ABSOLUTE_PATH (f)
>   #endif
>   
>   #define IS_DIR_SEPARATOR_1(dos_based, c)				\
> @@ -67,6 +69,8 @@ extern "C" {
>   
>   #define IS_DOS_DIR_SEPARATOR(c) IS_DIR_SEPARATOR_1 (1, c)
>   #define IS_DOS_ABSOLUTE_PATH(f) IS_ABSOLUTE_PATH_1 (1, f)
> +#define IS_DOS_REAL_ABSOLUTE_PATH(f) \
> +  ((f)[0] && (f)[1] == ':' && ((f)[2] == '/' || (f)[2] == '\\'))
>   #define HAS_DOS_DRIVE_SPEC(f) HAS_DRIVE_SPEC_1 (1, f)
>   
>   #define IS_UNIX_DIR_SEPARATOR(c) IS_DIR_SEPARATOR_1 (0, c)

-- 
Nathan Sidwell


  reply	other threads:[~2022-11-03 14:17 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-28  9:15 Torbjörn SVENSSON
2022-11-03 14:17 ` Nathan Sidwell [this message]
2022-11-03 15:06   ` Torbjorn SVENSSON
2022-11-07 23:03     ` Nathan Sidwell
2022-11-08 10:18       ` Torbjorn SVENSSON
2022-11-08 12:10         ` Nathan Sidwell

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