Hi!
.debug_loc section format only uses 2 byte long size field for expressions,
therefore we can't emit >= 64KB expressions.
Unfortunately from time to time we do generate them, I hope Alex will look
at how to prevent that from happening at var-tracking time, but still
this isn't something we should assert on. The following patch drops them
on the floor, it is questionable how much useful would they be compared to
their huge size, another alternative would be to create
DW_TAG_dwarf_procedure for them or for portions thereof (for subexpressions
it would be even a potential nice debug info shrinking method, but would
mean a lot of work and gdb support isn't there yet).
So, for the time being I'm suggesting to just don't emit anything.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2012-01-04 Jakub Jelinek <ja...@redhat.com>
PR debug/51695
* dwarf2out.c (output_loc_list): For now drop >= 64KB expressions
in .debug_loc on the floor.
* gcc.dg/pr51695.c: New test.
--- gcc/dwarf2out.c.jj 2012-01-03 16:22:48.000000000 +0100
+++ gcc/dwarf2out.c 2012-01-04 16:01:19.522191886 +0100
@@ -8166,6 +8166,13 @@ output_loc_list (dw_loc_list_ref list_he
/* Don't output an entry that starts and ends at the same address. */
if (strcmp (curr->begin, curr->end) == 0 && !curr->force)
continue;
+ size = size_of_locs (curr->expr);
+ /* If the expression is too large, drop it on the floor. We could
+ perhaps put it into DW_TAG_dwarf_procedure and refer to that
+ in the expression, but >= 64KB expressions for a single value
+ in a single range are unlikely very useful. */
+ if (size > 0xffff)
+ continue;
if (!have_multiple_function_sections)
{
dw2_asm_output_delta (DWARF2_ADDR_SIZE, curr->begin, curr->section,
@@ -8184,7 +8191,6 @@ output_loc_list (dw_loc_list_ref list_he
"Location list end address (%s)",
list_head->ll_symbol);
}
- size = size_of_locs (curr->expr);
/* Output the block length for this list of location operations. */
gcc_assert (size <= 0xffff);
--- gcc/testsuite/gcc.dg/pr51695.c.jj 2012-01-04 16:04:51.990964287 +0100
+++ gcc/testsuite/gcc.dg/pr51695.c 2012-01-04 16:03:16.000000000 +0100
@@ -0,0 +1,52 @@
+/* PR debug/51695 */
+/* { dg-do compile { target { int32plus } } } */
+/* { dg-options "-O2 -g" } */
+
+typedef struct
+{
+ struct { unsigned int t1, t2, t3, t4, t5, t6; } t;
+ int p;
+ struct { double X, Y, Z; } r;
+} T;
+typedef struct { T *h; } S;
+
+static unsigned int v = 0x12345678;
+
+int
+foo (void)
+{
+ v = (v & 0x80000000) ? ((v << 1) ^ 0xa398655d) : (v << 1);
+ return 0;
+}
+
+double
+bar (void)
+{
+ unsigned int o;
+ v = (v & 0x80000000) ? ((v << 1) ^ 0xa398655d) : (v << 1);
+ o = v & 0xffff;
+ return (double) o / 32768.0;
+}
+
+int
+baz (void)
+{
+ foo ();
+ return 0;
+}
+
+void
+test (S *x)
+{
+ T *t = x->h;
+ t->t.t1 = foo ();
+ t->t.t2 = foo ();
+ t->t.t3 = foo ();
+ t->t.t4 = foo ();
+ t->t.t5 = foo ();
+ t->t.t6 = foo ();
+ t->p = baz ();
+ t->r.X = bar ();
+ t->r.Y = bar ();
+ t->r.Z = bar ();
+}
Jakub
