PING [PATCH v3] c++: Allow module name to be a single letter on Windows

[Torbjorn SVENSSON <torbjorn.svensson@foss.st.com>]

Hi,

Ping, https://gcc.gnu.org/pipermail/gcc-patches/2022-November/606528.html

Kind regards,
Torbjörn

On 2022-11-17 14:20, Torbjörn SVENSSON wrote:
> v1 -> v2:
> Paths without "C:" part can still be absolute if they start with / or
> \ on Windows.
> 
> v2 -> v3:
> Use alternative approach by having platform specific code in module.cc.
> 
> Truth table for the new expression:
> c:\foo     -> true
> c:/foo     -> true
> /foo       -> true
> \foo       -> true
> c:foo      -> false
> foo        -> false
> ./foo      -> true
> .\foo      -> true
> 
> 
> Ok for trunk?
> 
> ---
> 
> 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.
> 
> gcc/cp/ChangeLog:
> 
> 	* module.cc: On Windows, 'A:Foo' is supposed to be a module
> 	and not a path.
> 
> Tested on Windows with arm-none-eabi for Cortex-M3 in gcc-11 tree.
> 
> Co-Authored-By: Yvan ROUX <yvan.roux@foss.st.com>
> Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
> ---
>   gcc/cp/module.cc | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 0e9af318ba4..fa41a86213f 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -13960,7 +13960,15 @@ 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))
> +  /* On DOS based file systems, there is an ambiguity with A:B which can be
> +     interpreted as a module Module:Partition or Drive:PATH.  Interpret strings
> +     which clearly starts as pathnames as header-names and everything else is
> +     treated as a (possibly malformed) named moduled.  */
> +  if (IS_DIR_SEPARATOR (ptr[ptr[0] == '.']) // ./FOO or /FOO
> +#if HAVE_DOS_BASED_FILE_SYSTEM
> +      || (HAS_DRIVE_SPEC (ptr) && IS_DIR_SEPARATOR (ptr[2])) // A:/FOO
> +#endif
> +      || false)
>       /* A header name.  */
>       return get_module (build_string (strlen (ptr), ptr));
>