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Fix libiberty link failures in LTO mode for MinGW

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The test for the presence of variables (really symbols) does not work
when you add -Ox -flto to CFLAGS:

  for v in $vars; do
    AC_MSG_CHECKING([for $v])
    AC_CACHE_VAL(libiberty_cv_var_$v,
      [AC_LINK_IFELSE([AC_LANG_PROGRAM([[int *p;]],[[extern int $v [];
                                         p = $v;]])],
                      [eval "libiberty_cv_var_$v=yes"],
                      [eval "libiberty_cv_var_$v=no"])])
    if eval "test \"`echo '$libiberty_cv_var_'$v`\" = yes"; then
      AC_MSG_RESULT(yes)
      AC_DEFINE_UNQUOTED($n)
    else
      AC_MSG_RESULT(no)
    fi
  done

because the assignment to 'p' is optimized away by LTO.  This is visible
on MinGW platforms in the form of a link failure for sys_siglist.

There is another link failures for stpcpy: the symbol is both referenced
by libiberty's pex-win32.c and provided by libiberty's stpcpy.c, so it
needs to have a linkage to be resolved in LTO mode.

libiberty/
	* configure.ac: Make test for variables more robust.
	* configure: Regenerate.
gcc/
	* builtins.c (builtin_with_linkage_p): Return true for stp[n]cpy.
	* symtab.c (symtab_node::output_to_lto_symbol_table_p): Tidy up.
This commit is contained in:
Eric Botcazou 2021-05-04 12:40:42 +02:00
parent 1b0f570009
commit f418bc3cd1
4 changed files with 14 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
gcc/builtins.c
View File

@ -14480,8 +14480,8 @@ target_char_cst_p (tree t, char *p)
}
/* Return true if the builtin DECL is implemented in a standard library.
Otherwise returns false which doesn't guarantee it is not (thus the list of
handled builtins below may be incomplete). */
Otherwise return false which doesn't guarantee it is not (thus the list
of handled builtins below may be incomplete). */
bool
builtin_with_linkage_p (tree decl)
@ -14560,6 +14560,14 @@ builtin_with_linkage_p (tree decl)
CASE_FLT_FN (BUILT_IN_TRUNC):
CASE_FLT_FN_FLOATN_NX (BUILT_IN_TRUNC):
return true;
case BUILT_IN_STPCPY:
case BUILT_IN_STPNCPY:
/* stpcpy is both referenced in libiberty's pex-win32.c and provided
by libiberty's stpcpy.c for MinGW targets so we need to return true
in order to be able to build libiberty in LTO mode for them. */
return true;
default:
break;
}

5
gcc/symtab.c
View File

@ -2526,10 +2526,7 @@ symtab_node::output_to_lto_symbol_table_p (void)
in libraries so make sure to output references into the symbol table to
make those libraries referenced. Note this is incomplete handling for
now and only covers math functions. */
if (builtin_with_linkage_p (decl))
return true;
else
return false;
return builtin_with_linkage_p (decl);
}
/* We have real symbol that should be in symbol table. However try to trim

4
libiberty/configure vendored
View File

@ -7049,11 +7049,11 @@ else
fi
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
int *p;
extern int $v [];
int
main ()
{
extern int $v []; p = $v;
if ($v [0]) return 1;
;
return 0;
}

2
libiberty/configure.ac
View File

@ -665,7 +665,7 @@ if test -z "${setobjs}"; then
for v in $vars; do
AC_MSG_CHECKING([for $v])
AC_CACHE_VAL(libiberty_cv_var_$v,
[AC_LINK_IFELSE([AC_LANG_PROGRAM([[int *p;]],[[extern int $v []; p = $v;]])],
[AC_LINK_IFELSE([AC_LANG_PROGRAM([[extern int $v [];]],[[if ($v [0]) return 1;]])],
[eval "libiberty_cv_var_$v=yes"],
[eval "libiberty_cv_var_$v=no"])])
if eval "test \"`echo '$libiberty_cv_var_'$v`\" = yes"; then