From 6df97c56ea0f3086c96743ec47148ee69fd8cf71 Mon Sep 17 00:00:00 2001 From: Kavitha Natarajan Date: Tue, 14 Jun 2022 10:37:46 +0530 Subject: [PATCH] Debug support for global alias variable Starting with (future) Clang 15 (since https://reviews.llvm.org/D120989), Clang emits the DWARF information of global alias variables as DW_TAG_imported_declaration. However, GDB does not handle it. It incorrectly always reads this tag as C++/Fortran imported declaration (type alias, namespace alias and Fortran module). This commit adds support to handle this tag as an alias variable. This change fixes the failures in the gdb.base/symbol-alias.exp testcase with current git Clang. This testcase is also updated to test nested (recursive) aliases. --- gdb/dwarf2/read.c | 63 ++++++++++++++++--------- gdb/testsuite/gdb.base/symbol-alias.exp | 63 +++++++++++++++++++++++-- gdb/testsuite/gdb.base/symbol-alias2.c | 12 +++++ 3 files changed, 114 insertions(+), 24 deletions(-) diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c index 64cb8d421b9..e22e09b4e2b 100644 --- a/gdb/dwarf2/read.c +++ b/gdb/dwarf2/read.c @@ -894,6 +894,10 @@ static void build_type_psymtabs_reader (cutu_reader *reader, static void dwarf2_build_psymtabs_hard (dwarf2_per_objfile *per_objfile); +static void var_decode_location (struct attribute *attr, + struct symbol *sym, + struct dwarf2_cu *cu); + static unsigned int peek_abbrev_code (bfd *, const gdb_byte *); static const gdb_byte *read_attribute (const struct die_reader_specs *, @@ -1071,7 +1075,7 @@ static struct using_direct **using_directives (struct dwarf2_cu *cu); static void read_import_statement (struct die_info *die, struct dwarf2_cu *); -static int read_namespace_alias (struct die_info *die, struct dwarf2_cu *cu); +static bool read_alias (struct die_info *die, struct dwarf2_cu *cu); static struct type *read_module_type (struct die_info *die, struct dwarf2_cu *cu); @@ -8664,9 +8668,10 @@ process_die (struct die_info *die, struct dwarf2_cu *cu) break; case DW_TAG_imported_declaration: cu->processing_has_namespace_info = true; - if (read_namespace_alias (die, cu)) + if (read_alias (die, cu)) break; - /* The declaration is not a global namespace alias. */ + /* The declaration is neither a global namespace nor a variable + alias. */ /* Fall through. */ case DW_TAG_imported_module: cu->processing_has_namespace_info = true; @@ -9134,18 +9139,18 @@ dwarf2_physname (const char *name, struct die_info *die, struct dwarf2_cu *cu) return retval; } -/* Inspect DIE in CU for a namespace alias. If one exists, record - a new symbol for it. +/* Inspect DIE in CU for a namespace alias or a variable with alias + attribute. If one exists, record a new symbol for it. - Returns 1 if a namespace alias was recorded, 0 otherwise. */ + Returns true if an alias was recorded, false otherwise. */ -static int -read_namespace_alias (struct die_info *die, struct dwarf2_cu *cu) +static bool +read_alias (struct die_info *die, struct dwarf2_cu *cu) { struct attribute *attr; - /* If the die does not have a name, this is not a namespace - alias. */ + /* If the die does not have a name, this is neither a namespace + alias nor a variable alias. */ attr = dwarf2_attr (die, DW_AT_name, cu); if (attr != NULL) { @@ -9171,26 +9176,42 @@ read_namespace_alias (struct die_info *die, struct dwarf2_cu *cu) { complaint (_("DIE at %s has too many recursively imported " "declarations"), sect_offset_str (d->sect_off)); - return 0; + return false; } if (attr != NULL) { struct type *type; - sect_offset sect_off = attr->get_ref_die_offset (); - - type = get_die_type_at_offset (sect_off, cu->per_cu, cu->per_objfile); - if (type != NULL && type->code () == TYPE_CODE_NAMESPACE) + if (d->tag == DW_TAG_variable) { - /* This declaration is a global namespace alias. Add - a symbol for it whose type is the aliased namespace. */ - new_symbol (die, type, cu); - return 1; + /* This declaration is a C/C++ global variable alias. + Add a symbol for it whose type is the same as the + aliased variable's. */ + type = die_type (d, imported_cu); + struct symbol *sym = new_symbol (die, type, cu); + attr = dwarf2_attr (d, DW_AT_location, imported_cu); + sym->set_aclass_index (LOC_UNRESOLVED); + if (attr != nullptr) + var_decode_location (attr, sym, cu); + return true; + } + else + { + sect_offset sect_off = attr->get_ref_die_offset (); + type = get_die_type_at_offset (sect_off, cu->per_cu, + cu->per_objfile); + if (type != nullptr && type->code () == TYPE_CODE_NAMESPACE) + { + /* This declaration is a global namespace alias. Add + a symbol for it whose type is the aliased + namespace. */ + new_symbol (die, type, cu); + return true; + } } } } - - return 0; + return false; } /* Return the using directives repository (global or local?) to use in the diff --git a/gdb/testsuite/gdb.base/symbol-alias.exp b/gdb/testsuite/gdb.base/symbol-alias.exp index 289f49bbc3f..9cc26bb66e5 100644 --- a/gdb/testsuite/gdb.base/symbol-alias.exp +++ b/gdb/testsuite/gdb.base/symbol-alias.exp @@ -15,6 +15,9 @@ # along with this program. If not, see . standard_testfile symbol-alias.c symbol-alias2.c +# Clang versions prior to v15 do not emit debug info for aliases. +set old_clang [expr [test_compiler_info {clang-1[0-4]-*-*}] \ + || [test_compiler_info {clang-[1-9]-*}]] if { [prepare_for_testing "failed to prepare" ${testfile} [list $srcfile $srcfile2]] } { return -1 @@ -30,7 +33,61 @@ foreach f {"func" "func_alias"} { gdb_test "p *${f}()" "= {field1 = 1, field2 = 2}" } -# Variables. -foreach v {"g_var_s" "g_var_s_alias"} { - gdb_test "p $v" "= {field1 = 1, field2 = 2}" +# Extern global variable. +gdb_test "p g_var_s" "= {field1 = 1, field2 = 2}" +foreach v {"g_var_s_alias" "g_var_s_alias2"} { + gdb_test_multiple "p $v" "print alias variable $v" { + -re -wrap " = {field1 = 1, field2 = 2}" { + pass $gdb_test_name + } + -re -wrap "has unknown type; cast it to its declared type" { + if { $old_clang } { + xfail $gdb_test_name + } else { + fail $gdb_test_name + } + } + } +} + +# Static global variable. +gdb_test "p g_var" " = 1" +gdb_test_multiple "p g_var_alias" "print alias of static variable" { + -re -wrap " = 1" { + pass $gdb_test_name + } + -re -wrap "has unknown type; cast it to its declared type" { + if { $old_clang } { + xfail $gdb_test_name + } else { + fail $gdb_test_name + } + } +} + +# Alias of a variable that is declared later in the scope. +gdb_test "p g_def_var" " = 2" +gdb_test_multiple "p g_def_var_alias" "print g_def_var_alias" { + -re -wrap " = 2" { + pass $gdb_test_name + } + -re -wrap "has unknown type; cast it to its declared type" { + if { $old_clang } { + xfail $gdb_test_name + } else { + fail $gdb_test_name + } + } +} +gdb_test_multiple "p g_def_var_alias2" "print g_def_var_alias2" { + -re -wrap " = 2" { + pass $gdb_test_name + } + -re -wrap "has unknown type; cast it to its declared type" { + if { $old_clang } { + xfail $gdb_test_name + } else { + fail $gdb_test_name + } + } } diff --git a/gdb/testsuite/gdb.base/symbol-alias2.c b/gdb/testsuite/gdb.base/symbol-alias2.c index 34f4e121e25..c1c0413ed60 100644 --- a/gdb/testsuite/gdb.base/symbol-alias2.c +++ b/gdb/testsuite/gdb.base/symbol-alias2.c @@ -23,6 +23,8 @@ struct S struct S g_var_s = { 1, 2 }; +static int g_var = 1; + #ifdef __cplusplus /* So that the alias attribute below work without having to figure out this function's mangled name. */ @@ -38,3 +40,13 @@ func (void) struct S *func_alias (void) __attribute__ ((alias ("func"))); extern struct S g_var_s_alias __attribute__ ((alias ("g_var_s"))); + +extern struct S g_var_s_alias2 __attribute__ ((alias ("g_var_s_alias"))); + +extern int g_var_alias __attribute__ ((alias ("g_var"))); + +extern int g_def_var_alias __attribute__ ((alias ("g_def_var"))); + +int g_def_var = 2; + +extern int g_def_var_alias2 __attribute__ ((alias ("g_def_var_alias"))); -- 2.30.2