[Issue 23025] New: ImportC: duplicate symbol for declaration and definition of variable

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23025

          Issue ID: 23025
           Summary: ImportC: duplicate symbol for declaration and
                    definition of variable
           Product: D
           Version: D2
          Hardware: All
                OS: Mac OS X
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: dave287091 at gmail.com

The following C program will fail to link with a duplicate symbol error.

```
const char *s; // tentative definition
const char *s = “hello”; // definition
int puts(const char*);
int main(void){
    puts(s);
    return 0
}
```

duplicate symbol '_s' in:
    dup.o
ld: 1 duplicate symbol for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Error: linker exited with status 1

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