ld resolving different types

[Norman Goldstein]

LD version:
   GNU ld version 2.31.1-37.fc30

Platform:
   Linux 5.4.17-100.fc30.x86_64 #1 SMP     x86_64 x86_64 x86_64 GNU/Linux

Compile/Link command:
    gcc tlink.cpp tlink2.cpp -o tlink -lstdc++

The programs compiles and links without warning or error, but resolves
/extern int foo/ with /double foo/.  The result of running the program
is, of course, garbage:

foo= -858993459

The program contains only 1 definition for foo (the extern statement is
a declaration), so the program is not violating the One Definition Rule.

Thank you.

[Andreas Schwab]

This violates the rule on type identity [basic.link], no diagnostic required.

Andreas.