From f73e424f7bb51d4a5164320107f386b8fec34f4b Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Tue, 9 Feb 2021 12:15:39 -0700 Subject: [PATCH] Avoid crash from coerce_unspec_val_to_type With a certain Ada program, ada-lang.c:coerce_unspec_val_to_type can cause a crash. This function may copy a value, and in the particular case in the crash, the new value's type is smaller than the original type. This causes coerce_unspec_val_to_type to create a lazy value -- but the original value is also not_lval, so later, when the value is un-lazied, gdb asserts. As with the previous patch, we believe there is a compiler bug here, but it is difficult to reproduce, so we're not completely certain. In the particular case we saw, the original value has record type, and the record holds some variable-length arrays. This leads to the type's length being 0. At the same time, the value is optimized out. This patch changes coerce_unspec_val_to_type to handle an optimized-out value correctly. It also slightly restructures this code to avoid a crash should a not_lval value wind up here. This is a purely defensive change. This change also made it clear that value_contents_copy_raw can now be made static, so that is also done. gdb/ChangeLog 2021-02-09 Tom Tromey * ada-lang.c (coerce_unspec_val_to_type): Avoid making lazy not_lval value. * value.c (value_contents_copy_raw): Now static. * value.h (value_contents_copy_raw): Don't declare. --- gdb/ChangeLog | 7 +++++++ gdb/ada-lang.c | 10 +++++++--- gdb/value.c | 2 +- gdb/value.h | 3 --- 4 files changed, 15 insertions(+), 7 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 6470c996a3..5c66f99e81 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,10 @@ +2021-02-09 Tom Tromey + + * ada-lang.c (coerce_unspec_val_to_type): Avoid making lazy + not_lval value. + * value.c (value_contents_copy_raw): Now static. + * value.h (value_contents_copy_raw): Don't declare. + 2021-02-09 Tom Tromey * gdbtypes.c (resolve_dynamic_struct): Handle structure with no diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c index 70296f9779..416a45be58 100644 --- a/gdb/ada-lang.c +++ b/gdb/ada-lang.c @@ -601,13 +601,17 @@ coerce_unspec_val_to_type (struct value *val, struct type *type) trying to allocate some memory for it. */ ada_ensure_varsize_limit (type); - if (value_lazy (val) - || TYPE_LENGTH (type) > TYPE_LENGTH (value_type (val))) + if (value_optimized_out (val)) + result = allocate_optimized_out_value (type); + else if (value_lazy (val) + /* Be careful not to make a lazy not_lval value. */ + || (VALUE_LVAL (val) != not_lval + && TYPE_LENGTH (type) > TYPE_LENGTH (value_type (val)))) result = allocate_value_lazy (type); else { result = allocate_value (type); - value_contents_copy_raw (result, 0, val, 0, TYPE_LENGTH (type)); + value_contents_copy (result, 0, val, 0, TYPE_LENGTH (type)); } set_value_component_location (result, val); set_value_bitsize (result, value_bitsize (val)); diff --git a/gdb/value.c b/gdb/value.c index 4135d5ec33..bddf9a4792 100644 --- a/gdb/value.c +++ b/gdb/value.c @@ -1304,7 +1304,7 @@ value_ranges_copy_adjusted (struct value *dst, int dst_bit_offset, It is assumed the contents of DST in the [DST_OFFSET, DST_OFFSET+LENGTH) range are wholly available. */ -void +static void value_contents_copy_raw (struct value *dst, LONGEST dst_offset, struct value *src, LONGEST src_offset, LONGEST length) { diff --git a/gdb/value.h b/gdb/value.h index 39e94f45ea..60a831c38c 100644 --- a/gdb/value.h +++ b/gdb/value.h @@ -739,9 +739,6 @@ extern struct value *allocate_value_lazy (struct type *type); extern void value_contents_copy (struct value *dst, LONGEST dst_offset, struct value *src, LONGEST src_offset, LONGEST length); -extern void value_contents_copy_raw (struct value *dst, LONGEST dst_offset, - struct value *src, LONGEST src_offset, - LONGEST length); extern struct value *allocate_repeat_value (struct type *type, int count); -- 2.34.1