[Bug ld/26580] New: Size and alignment from as-needed shared library bss symbols affect commons

[amodra at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26580

            Bug ID: 26580
           Summary: Size and alignment from as-needed shared library bss
                    symbols affect commons
           Product: binutils
           Version: 2.36 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: amodra at gmail dot com
  Target Milestone: ---

An as-needed shared library that isn't needed can affect common symbol size and
alignment.

cat > a.c <<\EOF
#include <stdio.h>

extern void __attribute__ ((weak)) foo (void);

char x, y, z;

long
lowest_align (void *a, void *b, void *c)
{
  unsigned long bits = (long) a | (long) b | (long) c;
  return bits & -bits;
}

int
main (void)
{
  printf ("library %sloaded\n", &foo ? "" : "not ");
  printf ("alignment %ld\n", lowest_align (&x, &y, &z));
  return 0;
}
EOF
cat > b.c <<\EOF
long long x, y, z;

void foo (void) {}
EOF
gcc -O2 -fpic -fcommon -shared -o libb.so b.c
gcc -O2 -fpic -fcommon -o y1 a.c -Wl,--no-as-needed,-R,. libb.so
./y1
library loaded
alignment 8
gcc -O2 -fpic -fcommon -o y2 a.c -Wl,--as-needed,-R,. libb.so
./y2
library not loaded
alignment 8
gcc -O2 -fpic -fcommon -o y3 a.c
./y3
library not loaded
alignment 1

I reckon y2 and y3 should print the same result.

-- 
You are receiving this mail because:
You are on the CC list for the bug.