[Bug lto/96969] New: ODR violations do not list the translation unit

[alan at octopull dot co.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96969

            Bug ID: 96969
           Summary: ODR violations do not list the translation unit
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alan at octopull dot co.uk
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

ODR violations can occur in structures defined in headers whose contents depend
on the inclusion context. For example:

./include/platform/mir/graphics/egl_extensions.h:164:12: error: type ‘struct
PlatformBaseEXT’ violates the C++ One Definition Rule [-Werror=odr]
./include/platform/mir/graphics/egl_extensions.h:164:12: note: a different type
is defined in another translation unit
./include/platform/mir/graphics/egl_extensions.h:168:47: note: the first
difference of corresponding definitions is field ‘eglGetPlatformDisplay’
./include/platform/mir/graphics/egl_extensions.h:168:47: note: a field with
different name is defined in another translation unit

The debug info in the .o should include the name of the "top level" file for
the translation unit, even if the path from that file to a specific location in
a header isn't stored. Alternatively, the name of the .o file would be helpful.

Please add some information to the diagnostic messages that identifies the
translation units that cause the ODR violation.