Re: [PATCHv2] gdb/fortran: Use floatformats_ia64_quad for fortran 16-byte floats

[Tom Tromey <tromey@adacore.com>]

>>>>> "Andrew" == Andrew Burgess <andrew.burgess@embecosm.com> writes:

>> This new version moves the use of floatformats_ia64_quad out of
>> f-lang.c, which I think is an improvement.  With this done I plan to
>> push this patch shortly unless anyone complains.

Andrew> This has now been pushed.

This caused a crash while testing gdb master using the internal AdaCore
test suite.

In particular what happened is that the ARM target (in fact many
targets) uses default_floatformat_for_type, returns NULL.  Then, if
build_fortran_types is called, it will crash gdb in arch_float_type:

    (top) bt
    #0  0x0000000000b4e3b1 in arch_float_type (gdbarch=0x32ef480, bit=128, name=0x1617675 "real*16", floatformats=0x0)
        at ../../binutils-gdb/gdb/gdbtypes.c:5169
    #1  0x0000000000b14b11 in build_fortran_types (gdbarch=0x32ef480) at ../../binutils-gdb/gdb/f-lang.c:735
    #2  0x0000000000b40d64 in gdbarch_data (gdbarch=0x32ef480, data=0x2d84bc0) at ../../binutils-gdb/gdb/gdbarch.c:5269
    #3  0x0000000000b14bb5 in builtin_f_type (gdbarch=0x32ef480) at ../../binutils-gdb/gdb/f-lang.c:755
    #4  0x0000000000b1378e in f_language_arch_info (gdbarch=0x32ef480, lai=0x33155e8) at ../../binutils-gdb/gdb/f-lang.c:171
    #5  0x0000000000be010d in language_gdbarch_post_init (gdbarch=0x32ef480) at ../../binutils-gdb/gdb/language.c:978
    #6  0x0000000000b40d64 in gdbarch_data (gdbarch=0x32ef480, data=0x31a43d0) at ../../binutils-gdb/gdb/gdbarch.c:5269
    #7  0x0000000000be0140 in language_string_char_type (la=0x15a20e0 <ada_language_defn>, gdbarch=0x32ef480)
        at ../../binutils-gdb/gdb/language.c:990
    #8  0x00000000008ac86c in type_char (par_state=0x7fffffffd400) at ../../binutils-gdb/gdb/ada-exp.y:1453
    #9  0x00000000008a7d85 in ada_yylex () at ../../binutils-gdb/gdb/ada-lex.l:151

In this case it happens via the Ada parser, but it can happen in many
ways, I think.

I'm testing the appended but I'm not really sure this is the best
approach.

Tom

diff --git a/gdb/f-lang.c b/gdb/f-lang.c
index 097e8906d1f..5c8eeab6f6b 100644
--- a/gdb/f-lang.c
+++ b/gdb/f-lang.c
@@ -731,8 +731,12 @@ build_fortran_types (struct gdbarch *gdbarch)
     = arch_float_type (gdbarch, gdbarch_double_bit (gdbarch),
 		       "real*8", gdbarch_double_format (gdbarch));
   auto fmt = gdbarch_floatformat_for_type (gdbarch, "real(kind=16)", 128);
-  builtin_f_type->builtin_real_s16
-    = arch_float_type (gdbarch, 128, "real*16", fmt);
+  if (fmt != nullptr)
+    builtin_f_type->builtin_real_s16
+      = arch_float_type (gdbarch, 128, "real*16", fmt);
+  else
+    builtin_f_type->builtin_real_s16
+      = arch_type (gdbarch, TYPE_CODE_ERROR, 128, "real*16");
 
   builtin_f_type->builtin_complex_s8
     = arch_complex_type (gdbarch, "complex*8",