gdb: Handle alignment for C++ structures with static members

In 'type_align' when computing the alignment of a structure we should
not consider the alignment of static structure members, these are
usually stored outside of the structure and therefore don't have any
impact on the structures alignment requirements.

I've extended the existing alignment calculating test to compile in
both C and C++ now so that we can create structures with static
members.

gdb/ChangeLog:

	* gdbtypes.c (type_align): Don't consider static members when
	computing structure alignment.

gdb/testsuite/ChangeLog:

	* gdb.base/align.exp: Extend to compile in both C and C++, and add
	tests for structs with static members.

4 files changed, 147 insertions, 60 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 07f3c47..ae9a68f 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2019-02-27  Andrew Burgess  <andrew.burgess@embecosm.com>
 
+	* gdbtypes.c (type_align): Don't consider static members when
+	computing structure alignment.
+
+2019-02-27  Andrew Burgess  <andrew.burgess@embecosm.com>
+
 	* arc-tdep.c (arc_type_align): Provide alignment for basic types,
 	return 0 for other types.
 	* arch-utils.c (default_type_align): Always return 0.
diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
index 63dec3c..b5f2692 100644
--- a/gdb/gdbtypes.c
+++ b/gdb/gdbtypes.c
@@ -3039,15 +3039,18 @@ type_align (struct type *type)
 	  }
 	for (unsigned i = 0; i < TYPE_NFIELDS (type); ++i)
 	  {
-	    ULONGEST f_align = type_align (TYPE_FIELD_TYPE (type, i));
-	    if (f_align == 0)
+	    if (!field_is_static (&TYPE_FIELD (type, i)))
 	      {
-		/* Don't pretend we know something we don't.  */
-		align = 0;
-		break;
+		ULONGEST f_align = type_align (TYPE_FIELD_TYPE (type, i));
+		if (f_align == 0)
+		  {
+		    /* Don't pretend we know something we don't.  */
+		    align = 0;
+		    break;
+		  }
+		if (f_align > align)
+		  align = f_align;
 	      }
-	    if (f_align > align)
-	      align = f_align;
 	  }
       }
       break;
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 693fc15..afe39de 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-02-27  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* gdb.base/align.exp: Extend to compile in both C and C++, and add
+	tests for structs with static members.
+
 2019-02-26  Tom Tromey  <tromey@adacore.com>
 
 	* gdb.python/py-value.exp (test_value_from_buffer): Check for
diff --git a/gdb/testsuite/gdb.base/align.exp b/gdb/testsuite/gdb.base/align.exp
index e7dcf2a..558625d 100644
--- a/gdb/testsuite/gdb.base/align.exp
+++ b/gdb/testsuite/gdb.base/align.exp
@@ -15,8 +15,15 @@
 
 # This file is part of the gdb testsuite
 
-# This tests that C11 _Alignof works in gdb, and that it agrees with
-# the compiler.
+# This tests that C11 _Alignof and C++11 alignof works in gdb, and
+# that it agrees with the compiler.
+
+# Only test C++ if we are able.  Always use C.
+if { [skip_cplus_tests] || [get_compiler_info "c++"] } {
+    set lang {c}
+} else {
+    set lang {c c++}
+}
 
 # The types we're going to test.
 
@@ -38,72 +45,139 @@ if {[has_int128_c]} {
     lappend typelist __int128
 }
 
-# Create the test file.
+# Build source file for testing alignment handling of language LANG.
+# Returns the name of the newly created source file.
+proc prepare_test_source_file { lang } {
+    global typelist
+
+    # Create the test file.
 
-set filename [standard_output_file align.c]
-set outfile [open $filename w]
+    if { $lang == "c++" } {
+	set suffix "cpp"
+	set align_func "alignof"
+    } else {
+	set suffix "c"
+	set align_func "_Alignof"
+    }
 
-# Prologue.
-puts -nonewline $outfile "#define DEF(T,U) struct align_pair_ ## T ## _x_ ## U "
-puts $outfile "{ T one; U two; }"
-puts $outfile "unsigned a_void = _Alignof(void);"
+    set filename [standard_output_file "$lang/align.$suffix"]
+    set outfile [open $filename w]
 
-# First emit single items.
-foreach type $typelist {
-    set utype [join [split $type] _]
-    if {$type != $utype} {
-	puts $outfile "typedef $type $utype;"
+    # Prologue.
+    puts -nonewline $outfile "#define DEF(T,U) struct align_pair_ ## T ## _x_ ## U "
+    puts $outfile "{ T one; U two; }"
+    if { $lang == "c++" } {
+	puts -nonewline $outfile "#define DEF_WITH_STATIC(T,U) struct align_pair_static_ ## T ## _x_ ## U "
+	puts $outfile "{ static T one; U two; }"
+    }
+    if { $lang == "c" } {
+	puts $outfile "unsigned a_void = ${align_func} (void);"
     }
-    puts $outfile "$type item_$utype;"
-    puts $outfile "unsigned a_$utype\n  = _Alignof ($type);"
-    set utype [join [split $type] _]
-}
 
-# Now emit all pairs.
-foreach type $typelist {
-    set utype [join [split $type] _]
-    foreach inner $typelist {
-	set uinner [join [split $inner] _]
-	puts $outfile "DEF ($utype, $uinner);"
-	set joined "${utype}_x_${uinner}"
-	puts $outfile "struct align_pair_$joined item_${joined};"
-	puts $outfile "unsigned a_${joined}"
-	puts $outfile "  = _Alignof (struct align_pair_${joined});"
+    # First emit single items.
+    foreach type $typelist {
+	set utype [join [split $type] _]
+	if {$type != $utype} {
+	    puts $outfile "typedef $type $utype;"
+	}
+	puts $outfile "$type item_$utype;"
+	if { $lang == "c" } {
+	    puts $outfile "unsigned a_$utype\n  = ${align_func} ($type);"
+	}
+	set utype [join [split $type] _]
     }
-}
 
-# Epilogue.
-puts $outfile {
-    int main() {
-	return 0;
+    # Now emit all pairs.
+    foreach type $typelist {
+	set utype [join [split $type] _]
+	foreach inner $typelist {
+	    set uinner [join [split $inner] _]
+	    puts $outfile "DEF ($utype, $uinner);"
+	    set joined "${utype}_x_${uinner}"
+	    puts $outfile "struct align_pair_$joined item_${joined};"
+	    puts $outfile "unsigned a_${joined}"
+	    puts $outfile "  = ${align_func} (struct align_pair_${joined});"
+
+	    if { $lang == "c++" } {
+		puts $outfile "DEF_WITH_STATIC ($utype, $uinner);"
+		set joined "${utype}_x_${uinner}"
+		puts $outfile "struct align_pair_static_$joined item_static_${joined};"
+		puts $outfile "unsigned a_static_${joined}"
+		puts $outfile "  = ${align_func} (struct align_pair_static_${joined});"
+	    }
+	}
     }
-}
 
-close $outfile
+    # Epilogue.
+    puts $outfile {
+	int main() {
+	    return 0;
+	}
+    }
 
-standard_testfile $filename
+    close $outfile
 
-if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug}]} {
-    return -1
+    return $filename
 }
 
-if {![runto_main]} {
-    perror "test suppressed"
-    return
-}
+# Run the alignment test for the language LANG.
+proc run_alignment_test { lang } {
+    global testfile srcfile typelist
+    global subdir
+
+    set filename [prepare_test_source_file $lang]
 
-foreach type $typelist {
-    set utype [join [split $type] _]
-    set expected [get_integer_valueof a_$utype 0]
-    gdb_test "print _Alignof($type)" " = $expected"
+    standard_testfile $filename
+    if {[prepare_for_testing "failed to prepare" "$lang/$testfile" $srcfile {debug}]} {
+	return -1
+    }
+
+    if {![runto_main]} {
+	perror "test suppressed"
+	return
+    }
+
+    if { $lang == "c++" } {
+	set align_func "alignof"
+    } else {
+	set align_func "_Alignof"
+    }
 
-    foreach inner $typelist {
-	set uinner [join [split $inner] _]
-	set expected [get_integer_valueof a_${utype}_x_${uinner} 0]
-	gdb_test "print _Alignof(struct align_pair_${utype}_x_${uinner})" \
-	    " = $expected"
+    foreach type $typelist {
+	set utype [join [split $type] _]
+	if { $lang == "c" } {
+	    set expected [get_integer_valueof a_$utype 0]
+	    gdb_test "print ${align_func}($type)" " = $expected"
+	}
+
+	foreach inner $typelist {
+	    set uinner [join [split $inner] _]
+	    set expected [get_integer_valueof a_${utype}_x_${uinner} 0]
+	    gdb_test "print ${align_func}(struct align_pair_${utype}_x_${uinner})" \
+		" = $expected"
+
+	    if { $lang == "c++" } {
+		set expected [get_integer_valueof a_static_${utype}_x_${uinner} 0]
+		gdb_test "print ${align_func}(struct align_pair_static_${utype}_x_${uinner})" \
+		    " = $expected"
+	    }
+	}
+    }
+
+    if { $lang == "c" } {
+	set expected [get_integer_valueof a_void 0]
+	gdb_test "print ${align_func}(void)" " = $expected"
     }
 }
 
-set expected [get_integer_valueof a_void 0]
-gdb_test "print _Alignof(void)" " = $expected"
+# Create nested 'c' and 'c++' directories within this tests directory.
+foreach l $lang {
+    set dir "$l"
+    remote_exec host "rm -rf [standard_output_file ${dir}]"
+    remote_exec host "mkdir -p [standard_output_file ${dir}]"
+}
+
+# Now run the test for each language.
+foreach_with_prefix l $lang {
+    run_alignment_test $l
+}