[Bug c++/69523] New: -Wliteral-suffix should not warn within namespace std

[eric at efcs dot ca]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69523

            Bug ID: 69523
           Summary: -Wliteral-suffix should not warn within namespace std
           Product: gcc
           Version: 5.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: eric at efcs dot ca
  Target Milestone: ---

Created attachment 37497
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37497&action=edit
reproducer.cpp

While developing for libc++ I enable warnings in the headers. Unfortunately
<string> always emits the warning:

> libcxx/include/string:4267:36: error: literal operator suffixes not preceded by ‘_’ are reserved for future standardization [-Werror]

Obviously this is a false positive. Since the warning is on by default and
-Wno-literal-suffix doesn't disable it, then it needs to ignore user defined
literals within namespace std.