From d8a5d6ee2fdfd0e8a0a9cc8386a5d0b580372f52 Mon Sep 17 00:00:00 2001 From: Joel Brobecker Date: Wed, 14 Mar 2012 01:38:58 +0000 Subject: [PATCH] ax-gdb: Do not treat enums and bools as integers. This patch fixes a problem when using gdb + gdbserver, and trying to break on a function when one of the (enum) parameters is equal to a certain value, and the size of that enum is 1 byte. (gdb) break mixed.adb:15 if light = green Breakpoint 2 at 0x402d5a: file mixed.adb, line 15. (gdb) cont Continuing. [Inferior 1 (process 9742) exited normally] The debugger should have stopped once when our function was call with light set to green. Here is what happens: Because we're using a recent GDBserver, GDB hands off the evaluation of the condition to GDBserver, by providing it in the Z0 packet. This is what GDB sends: $Z0,402d5a,1;X13,26000622100223ff1c16100219162022011327#cf I decoded the condition as follow: 260006 reg 6 -> push 2210 const8 0x10 -> push 02 add (stack now has 1 element equal to reg6 + 16) 23ff1c const16 0xff1c 1610 ext 16 (sign extend 16 bits) 02 add (stack now has 1 element equal to reg6 + 16 - 228) 19 ref32: Pop as addr, push 32bit value at addr. 1620 ext 32 (sign extend 32 bits) 2201 const8 0x01 13 equal 27 end The beginning of the agent expression can be explained by the address of symbol "light": (gdb) info addr light Symbol "light" is a variable at frame base reg $rbp offset 16+-228. However, the mistake is the "ext 32" operation (extend 32 bits), because our variable is *not* 32bits, only 8: (gdb) print light'size $5 = 8 But the reason why GDB decides to use a 32bit extension is because it overrides the symbol's type with a plain integer type in ax-gdb.c:gen_usual_unary... /* If the value is an enum or a bool, call it an integer. */ case TYPE_CODE_ENUM: case TYPE_CODE_BOOL: value->type = builtin_type (exp->gdbarch)->builtin_int; break; ... before calling require_rvalue. And of course, that causes the generator to generate a sizeof(int) extension of the result. One way to fix this would be to use an integer type of the correct size, but I do not understand why this is necessary. The two routines that use that information to generate the opcode down the line are gen_fetch (for a memory value), or gen_extend (for a register value). And they both have handling of enums and bools. So the fix we elected to implement was simply to remove that code. gdb/ChangeLog: * ax-gdb.c (gen_usual_unary): Remove special handling of enum and bool types. --- gdb/ChangeLog | 5 +++++ gdb/ax-gdb.c | 6 ------ 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index d941d33ac9..89a97236f1 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2012-03-13 Joel Brobecker + + * ax-gdb.c (gen_usual_unary): Remove special handling of + enum and bool types. + 2012-03-13 Joel Brobecker * ax-gdb.c (gen_fetch): Add handling for TYPE_CODE_RANGE types. diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c index 126a4e74d1..a76e781720 100644 --- a/gdb/ax-gdb.c +++ b/gdb/ax-gdb.c @@ -880,12 +880,6 @@ gen_usual_unary (struct expression *exp, struct agent_expr *ax, case TYPE_CODE_STRUCT: case TYPE_CODE_UNION: return; - - /* If the value is an enum or a bool, call it an integer. */ - case TYPE_CODE_ENUM: - case TYPE_CODE_BOOL: - value->type = builtin_type (exp->gdbarch)->builtin_int; - break; } /* If the value is an lvalue, dereference it. */ -- 2.34.1