[Bug ld/15323] New: Unable to redefine weak function in -flto incrementally-linked executable

[josh.m.conner at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=15323

             Bug #: 15323
           Summary: Unable to redefine weak function in -flto
                    incrementally-linked executable
           Product: binutils
           Version: 2.23
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
        AssignedTo: address@hidden
        ReportedBy: address@hidden
    Classification: Unclassified


If I have a weak function defined in an executable created with -flto -r, when
I try to redefine the function by re-linking with an object file containing a
non-weak definition of the same function, I get an error:

`foobar' referenced in section `.text.startup' of test-intermediate: defined in
discarded section `.text' of test.o (symbol from plugin)
collect2: error: ld returned 1 exit status

Here are some steps to reproduce, where gcc is using ld with the linker plugin
for lto:

$ cat test-weak.c
volatile int x;

__attribute__((weak))
void foobar (void) { x++; }

int main (void)
{
  foobar ();
  return 0;
}

$ cat test.c
extern volatile int x;

void foobar (void) { x--; }

$ gcc -flto -g -O2 -c -o test-weak.o test-weak.c
$ gcc -flto -g -O2 -c -o test.o test.c
$ gcc -flto -g -O2 -r -o test-intermediate test-weak.o -nostdlib
-nostartfiles
$ gcc -flto -g -O2 -o test test-intermediate test.o
`foobar' referenced in section `.text.startup' of test-intermediate: defined in
discarded section `.text' of test.o (symbol from plugin)
collect2: error: ld returned 1 exit status

Let me know if you need an example that is assembly-only, or if you need me to
verify with top-of-tree.

(Note that I can work around the error with -fno-use-linker-plugin, but I want
to use the linker plugin for whole program optimization purposes).

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