diff options
Diffstat (limited to 'gcc/java/expr.c')
| -rw-r--r-- | gcc/java/expr.c | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/gcc/java/expr.c b/gcc/java/expr.c index 785ccc4..c178552 100644 --- a/gcc/java/expr.c +++ b/gcc/java/expr.c @@ -130,6 +130,10 @@ static GTY(()) tree quick_stack; /* A free-list of unused permanent TREE_LIST nodes. */ static GTY((deletable)) tree tree_list_free_list; +/* The physical memory page size used in this computer. See + build_field_ref(). */ +static GTY(()) tree page_size; + /* The stack pointer of the Java virtual machine. This does include the size of the quick_stack. */ @@ -1678,11 +1682,28 @@ build_field_ref (tree self_value, tree self_class, tree name) } else { - int check = (flag_check_references - && ! (DECL_P (self_value) - && DECL_NAME (self_value) == this_identifier_node)); - tree base_type = promote_type (base_class); + + /* CHECK is true if self_value is not the this pointer. */ + int check = (! (DECL_P (self_value) + && DECL_NAME (self_value) == this_identifier_node)); + + /* Determine whether a field offset from NULL will lie within + Page 0: this is necessary on those GNU/Linux/BSD systems that + trap SEGV to generate NullPointerExceptions. + + We assume that Page 0 will be mapped with NOPERM, and that + memory may be allocated from any other page, so only field + offsets < pagesize are guaratneed to trap. We also assume + the smallest page size we'll encounter is 4k bytes. */ + if (check && ! flag_check_references && ! flag_indirect_dispatch) + { + tree field_offset = byte_position (field_decl); + if (! page_size) + page_size = size_int (4096); + check = ! INT_CST_LT_UNSIGNED (field_offset, page_size); + } + if (base_type != TREE_TYPE (self_value)) self_value = fold_build1 (NOP_EXPR, base_type, self_value); if (! flag_syntax_only && flag_indirect_dispatch) @@ -1708,6 +1729,7 @@ build_field_ref (tree self_value, tree self_class, tree name) field_offset); field_offset = fold (convert (sizetype, field_offset)); + self_value = java_check_reference (self_value, check); address = fold_build2 (PLUS_EXPR, build_pointer_type (TREE_TYPE (field_decl)), |