toolchain/musl/patches/001-eliminate-protected-visibility-data-in-libc.so-with-.patch

   1 From: Rich Felker <dalias@aerifal.cx>
   2 Date: Tue, 29 Sep 2015 02:44:05 +0000
   3 Subject: [PATCH] eliminate protected-visibility data in libc.so with vis.h
   4  preinclude
   5
   6 some newer binutils versions print scary warnings about protected data
   7 because most gcc versions fail to produce the right address
   8 references/relocations for such data that might be subject to copy
   9 relocations. originally vis.h explicitly assigned default visibility
  10 to all public data symbols to avoid this issue, but commit
  11 b8dda24fe1caa901a99580f7a52defb95aedb67c removed this treatment for
  12 stdin/out/err to work around a gcc 3.x bug, and since they don't
  13 actually need it (because taking their addresses is not valid C).
  14
  15 instead, a check for the gcc 3.x bug is added to the configure check
  16 for vis.h preinclude support; this feature will simply be disabled
  17 when using a buggy version of gcc.
  18 ---
  19
  20 --- a/configure
  21 +++ b/configure
  22 @@ -476,10 +476,18 @@ if test "x$visibility" = xauto ; then
  23  # - the -include option
  24  # - the attributes/pragmas used in vis.h
  25  # - linking code that takes the address of protected symbols
  26 +# - gcc 3.x bug that wrongly claims declarations mismatch
  27  printf "checking whether global visibility preinclude works... "
  28 -echo 'int (*fp)(void);' > "$tmpc"
  29 -echo 'int foo(void) { }' >> "$tmpc"
  30 -echo 'int bar(void) { fp = foo; return foo(); }' >> "$tmpc"
  31 +cat > "$tmpc" <<EOF
  32 +__attribute__((__visibility__("default")))
  33 +extern struct a *const x;
  34 +typedef struct a b;
  35 +extern b *const x;
  36 +b *const x;
  37 +int (*fp)(void);
  38 +int foo(void) { }
  39 +int bar(void) { fp = foo; return foo(); }
  40 +EOF
  41  if $CC $CFLAGS_C99FSE $CPPFLAGS $CFLAGS \
  42    -DSHARED -fPIC -I./src/internal -include vis.h \
  43    -nostdlib -shared -Wl,-Bsymbolic-functions \
  44 --- a/src/internal/vis.h
  45 +++ b/src/internal/vis.h
  46 @@ -12,6 +12,9 @@
  47   * exported data symbols. */
  48
  49  __attribute__((__visibility__("default")))
  50 +extern struct _IO_FILE *const stdin, *const stdout, *const stderr;
  51 +
  52 +__attribute__((__visibility__("default")))
  53  extern int optind, opterr, optopt, optreset, __optreset, getdate_err, h_errno, daylight, __daylight, signgam, __signgam;
  54
  55  __attribute__((__visibility__("default")))