+// A version script essentially maps a symbol name to a version tag
+// and an indication of whether symbol is global or local within that
+// version tag. Each symbol maps to at most one version tag.
+// Unfortunately, in practice, version scripts are ambiguous, and list
+// symbols multiple times. Thus, we have to document the matching
+// process.
+
+// This is a description of what the GNU linker does as of 2010-01-11.
+// It walks through the version tags in the order in which they appear
+// in the version script. For each tag, it first walks through the
+// global patterns for that tag, then the local patterns. When
+// looking at a single pattern, it first applies any language specific
+// demangling as specified for the pattern, and then matches the
+// resulting symbol name to the pattern. If it finds an exact match
+// for a literal pattern (a pattern enclosed in quotes or with no
+// wildcard characters), then that is the match that it uses. If
+// finds a match with a wildcard pattern, then it saves it and
+// continues searching. Wildcard patterns that are exactly "*" are
+// saved separately.
+
+// If no exact match with a literal pattern is ever found, then if a
+// wildcard match with a global pattern was found it is used,
+// otherwise if a wildcard match with a local pattern was found it is
+// used.
+
+// This is the result:
+// * If there is an exact match, then we use the first tag in the
+// version script where it matches.
+// + If the exact match in that tag is global, it is used.
+// + Otherwise the exact match in that tag is local, and is used.
+// * Otherwise, if there is any match with a global wildcard pattern:
+// + If there is any match with a wildcard pattern which is not
+// "*", then we use the tag in which the *last* such pattern
+// appears.
+// + Otherwise, we matched "*". If there is no match with a local
+// wildcard pattern which is not "*", then we use the *last*
+// match with a global "*". Otherwise, continue.
+// * Otherwise, if there is any match with a local wildcard pattern:
+// + If there is any match with a wildcard pattern which is not
+// "*", then we use the tag in which the *last* such pattern
+// appears.
+// + Otherwise, we matched "*", and we use the tag in which the
+// *last* such match occurred.
+
+// There is an additional wrinkle. When the GNU linker finds a symbol
+// with a version defined in an object file due to a .symver
+// directive, it looks up that symbol name in that version tag. If it
+// finds it, it matches the symbol name against the patterns for that
+// version. If there is no match with a global pattern, but there is
+// a match with a local pattern, then the GNU linker marks the symbol
+// as local.
+
+// We want gold to be generally compatible, but we also want gold to
+// be fast. These are the rules that gold implements:
+// * If there is an exact match for the mangled name, we use it.
+// + If there is more than one exact match, we give a warning, and
+// we use the first tag in the script which matches.
+// + If a symbol has an exact match as both global and local for
+// the same version tag, we give an error.
+// * Otherwise, we look for an extern C++ or an extern Java exact
+// match. If we find an exact match, we use it.
+// + If there is more than one exact match, we give a warning, and
+// we use the first tag in the script which matches.
+// + If a symbol has an exact match as both global and local for
+// the same version tag, we give an error.
+// * Otherwise, we look through the wildcard patterns, ignoring "*"
+// patterns. We look through the version tags in reverse order.
+// For each version tag, we look through the global patterns and
+// then the local patterns. We use the first match we find (i.e.,
+// the last matching version tag in the file).
+// * Otherwise, we use the "*" pattern if there is one. We give an
+// error if there are multiple "*" patterns.
+
+// At least for now, gold does not look up the version tag for a
+// symbol version found in an object file to see if it should be
+// forced local. There are other ways to force a symbol to be local,
+// and I don't understand why this one is useful.
+
+// Build a set of fast lookup tables for a version script.
+
+void
+Version_script_info::build_lookup_tables()
+{
+ size_t size = this->version_trees_.size();
+ for (size_t j = 0; j < size; ++j)
+ {
+ const Version_tree* v = this->version_trees_[j];
+ this->build_expression_list_lookup(v->local, v, false);
+ this->build_expression_list_lookup(v->global, v, true);
+ }
+}
+
+// If a pattern has backlashes but no unquoted wildcard characters,
+// then we apply backslash unquoting and look for an exact match.
+// Otherwise we treat it as a wildcard pattern. This function returns
+// true for a wildcard pattern. Otherwise, it does backslash
+// unquoting on *PATTERN and returns false. If this returns true,
+// *PATTERN may have been partially unquoted.
+
+bool
+Version_script_info::unquote(std::string* pattern) const
+{
+ bool saw_backslash = false;
+ size_t len = pattern->length();
+ size_t j = 0;
+ for (size_t i = 0; i < len; ++i)
+ {
+ if (saw_backslash)
+ saw_backslash = false;
+ else
+ {
+ switch ((*pattern)[i])
+ {
+ case '?': case '[': case '*':
+ return true;
+ case '\\':
+ saw_backslash = true;
+ continue;
+ default:
+ break;
+ }
+ }
+
+ if (i != j)
+ (*pattern)[j] = (*pattern)[i];
+ ++j;
+ }
+ return false;
+}
+
+// Add an exact match for MATCH to *PE. The result of the match is
+// V/IS_GLOBAL.
+
+void
+Version_script_info::add_exact_match(const std::string& match,
+ const Version_tree* v, bool is_global,
+ const Version_expression* ve,
+ Exact* pe)
+{
+ std::pair<Exact::iterator, bool> ins =
+ pe->insert(std::make_pair(match, Version_tree_match(v, is_global, ve)));
+ if (ins.second)
+ {
+ // This is the first time we have seen this match.
+ return;
+ }
+
+ Version_tree_match& vtm(ins.first->second);
+ if (vtm.real->tag != v->tag)
+ {
+ // This is an ambiguous match. We still return the
+ // first version that we found in the script, but we
+ // record the new version to issue a warning if we
+ // wind up looking up this symbol.
+ if (vtm.ambiguous == NULL)
+ vtm.ambiguous = v;
+ }
+ else if (is_global != vtm.is_global)
+ {
+ // We have a match for both the global and local entries for a
+ // version tag. That's got to be wrong.
+ gold_error(_("'%s' appears as both a global and a local symbol "
+ "for version '%s' in script"),
+ match.c_str(), v->tag.c_str());
+ }
+}
+
+// Build fast lookup information for EXPLIST and store it in LOOKUP.
+// All matches go to V, and IS_GLOBAL is true if they are global
+// matches.
+
+void
+Version_script_info::build_expression_list_lookup(
+ const Version_expression_list* explist,
+ const Version_tree* v,
+ bool is_global)
+{
+ if (explist == NULL)
+ return;
+ size_t size = explist->expressions.size();
+ for (size_t i = 0; i < size; ++i)
+ {
+ const Version_expression& exp(explist->expressions[i]);
+
+ if (exp.pattern.length() == 1 && exp.pattern[0] == '*')
+ {
+ if (this->default_version_ != NULL
+ && this->default_version_->tag != v->tag)
+ gold_warning(_("wildcard match appears in both version '%s' "
+ "and '%s' in script"),
+ this->default_version_->tag.c_str(), v->tag.c_str());
+ else if (this->default_version_ != NULL
+ && this->default_is_global_ != is_global)
+ gold_error(_("wildcard match appears as both global and local "
+ "in version '%s' in script"),
+ v->tag.c_str());
+ this->default_version_ = v;
+ this->default_is_global_ = is_global;
+ continue;
+ }
+
+ std::string pattern = exp.pattern;
+ if (!exp.exact_match)
+ {
+ if (this->unquote(&pattern))
+ {
+ this->globs_.push_back(Glob(&exp, v, is_global));
+ continue;
+ }
+ }
+
+ if (this->exact_[exp.language] == NULL)
+ this->exact_[exp.language] = new Exact();
+ this->add_exact_match(pattern, v, is_global, &exp,
+ this->exact_[exp.language]);
+ }
+}
+
+// Return the name to match given a name, a language code, and two
+// lazy demanglers.
+
+const char*
+Version_script_info::get_name_to_match(const char* name,
+ int language,
+ Lazy_demangler* cpp_demangler,
+ Lazy_demangler* java_demangler) const
+{
+ switch (language)
+ {
+ case LANGUAGE_C:
+ return name;
+ case LANGUAGE_CXX:
+ return cpp_demangler->get();
+ case LANGUAGE_JAVA:
+ return java_demangler->get();
+ default:
+ gold_unreachable();
+ }
+}
+
+// Look up SYMBOL_NAME in the list of versions. Return true if the
+// symbol is found, false if not. If the symbol is found, then if
+// PVERSION is not NULL, set *PVERSION to the version tag, and if
+// P_IS_GLOBAL is not NULL, set *P_IS_GLOBAL according to whether the
+// symbol is global or not.