diff options
Diffstat (limited to 'gdb/value.h')
| -rw-r--r-- | gdb/value.h | 158 |
1 files changed, 111 insertions, 47 deletions
diff --git a/gdb/value.h b/gdb/value.h index 843478b4766..5d4949c5794 100644 --- a/gdb/value.h +++ b/gdb/value.h @@ -33,6 +33,54 @@ struct language_defn; struct value_print_options; struct xmethod_worker; +/* Values can be partially 'optimized out' and/or 'unavailable'. + These are distinct states and have different string representations + and related error strings. + + 'unavailable' has a specific meaning in this context. It means the + value exists in the program (at the machine level), but GDB has no + means to get to it. Such a value is normally printed as + <unavailable>. Examples of how to end up with an unavailable value + would be: + + - We're inspecting a traceframe, and the memory or registers the + debug information says the value lives on haven't been collected. + + - We're inspecting a core dump, the memory or registers the debug + information says the value lives aren't present in the dump + (that is, we have a partial/trimmed core dump, or we don't fully + understand/handle the core dump's format). + + - We're doing live debugging, but the debug API has no means to + get at where the value lives in the machine, like e.g., ptrace + not having access to some register or register set. + + - Any other similar scenario. + + OTOH, "optimized out" is about what the compiler decided to generate + (or not generate). A chunk of a value that was optimized out does + not actually exist in the program. There's no way to get at it + short of compiling the program differently. + + A register that has not been saved in a frame is likewise considered + optimized out, except not-saved registers have a different string + representation and related error strings. E.g., we'll print them as + <not-saved> instead of <optimized out>, as in: + + (gdb) p/x $rax + $1 = <not saved> + (gdb) info registers rax + rax <not saved> + + If the debug info describes a variable as being in such a register, + we'll still print the variable as <optimized out>. IOW, <not saved> + is reserved for inspecting registers at the machine level. + + When comparing value contents, optimized out chunks, unavailable + chunks, and valid contents data are all considered different. See + value_contents_eq for more info. +*/ + /* The structure which defines the type of a value. It should never be possible for a program lval value to survive over a call to the inferior (i.e. to be put into the history list or an internal @@ -181,14 +229,6 @@ struct lval_funcs TOVAL is not considered as an lvalue. */ void (*write) (struct value *toval, struct value *fromval); - /* Check the validity of some bits in VALUE. This should return 1 - if all the bits starting at OFFSET and extending for LENGTH bits - are valid, or 0 if any bit is invalid. */ - int (*check_validity) (const struct value *value, int offset, int length); - - /* Return 1 if any bit in VALUE is valid, 0 if they are all invalid. */ - int (*check_any_valid) (const struct value *value); - /* If non-NULL, this is used to implement pointer indirection for this value. This method may return NULL, in which case value_ind will fall back to ordinary indirection. */ @@ -327,16 +367,29 @@ extern int value_fetch_lazy (struct value *val); exist in the program, at least partially. If the value is lazy, this may fetch it now. */ extern int value_optimized_out (struct value *value); -extern void set_value_optimized_out (struct value *value, int val); -/* Like value_optimized_out, but don't fetch the value even if it is - lazy. Mainly useful for constructing other values using VALUE as - template. */ -extern int value_optimized_out_const (const struct value *value); +/* Given a value, return true if any of the contents bits starting at + OFFSET and extending for LENGTH bits is optimized out, false + otherwise. */ + +extern int value_bits_any_optimized_out (const struct value *value, + int bit_offset, int bit_length); + +/* Like value_optimized_out, but return true iff the whole value is + optimized out. */ +extern int value_entirely_optimized_out (struct value *value); + +/* Mark VALUE's content bytes starting at OFFSET and extending for + LENGTH bytes as optimized out. */ + +extern void mark_value_bytes_optimized_out (struct value *value, + int offset, int length); + +/* Mark VALUE's content bits starting at OFFSET and extending for + LENGTH bits as optimized out. */ -/* Like value_optimized_out, but return false if any bit in the object - is valid. */ -extern int value_entirely_optimized_out (const struct value *value); +extern void mark_value_bits_optimized_out (struct value *value, + int offset, int length); /* Set or return field indicating whether a variable is initialized or not, based on debugging information supplied by the compiler. @@ -416,13 +469,6 @@ extern struct value *coerce_ref (struct value *value); extern struct value *coerce_array (struct value *value); /* Given a value, determine whether the bits starting at OFFSET and - extending for LENGTH bits are valid. This returns nonzero if all - bits in the given range are valid, zero if any bit is invalid. */ - -extern int value_bits_valid (const struct value *value, - int offset, int length); - -/* Given a value, determine whether the bits starting at OFFSET and extending for LENGTH bits are a synthetic pointer. */ extern int value_bits_synthetic_pointer (const struct value *value, @@ -473,35 +519,53 @@ extern void mark_value_bits_unavailable (struct value *value, its enclosing type chunk, you'd do: int len = TYPE_LENGTH (check_typedef (value_enclosing_type (val))); - value_available_contents (val, 0, val, 0, len); + value_contents_eq (val, 0, val, 0, len); + + Returns true iff the set of available/valid contents match. + + Optimized-out contents are equal to optimized-out contents, and are + not equal to non-optimized-out contents. - Returns true iff the set of available contents match. Unavailable - contents compare equal with unavailable contents, and different - with any available byte. For example, if 'x's represent an - unavailable byte, and 'V' and 'Z' represent different available - bytes, in a value with length 16: + Unavailable contente are equal to unavailable contents, and are not + equal to non-unavailable contents. - offset: 0 4 8 12 16 - contents: xxxxVVVVxxxxVVZZ + For example, if 'x's represent an unavailable byte, and 'V' and 'Z' + represent different available/valid bytes, in a value with length + 16: + + offset: 0 4 8 12 16 + contents: xxxxVVVVxxxxVVZZ then: - value_available_contents_eq(val, 0, val, 8, 6) => 1 - value_available_contents_eq(val, 0, val, 4, 4) => 1 - value_available_contents_eq(val, 0, val, 8, 8) => 0 - value_available_contents_eq(val, 4, val, 12, 2) => 1 - value_available_contents_eq(val, 4, val, 12, 4) => 0 - value_available_contents_eq(val, 3, val, 4, 4) => 0 - - We only know whether a value chunk is available if we've tried to - read it. As this routine is used by printing routines, which may - be printing values in the value history, long after the inferior is - gone, it works with const values. Therefore, this routine must not - be called with lazy values. */ - -extern int value_available_contents_eq (const struct value *val1, int offset1, - const struct value *val2, int offset2, - int length); + value_contents_eq(val, 0, val, 8, 6) => 1 + value_contents_eq(val, 0, val, 4, 4) => 0 + value_contents_eq(val, 0, val, 8, 8) => 0 + value_contents_eq(val, 4, val, 12, 2) => 1 + value_contents_eq(val, 4, val, 12, 4) => 0 + value_contents_eq(val, 3, val, 4, 4) => 0 + + If 'x's represent an unavailable byte, 'o' represents an optimized + out byte, in a value with length 8: + + offset: 0 4 8 + contents: xxxxoooo + + then: + + value_contents_eq(val, 0, val, 2, 2) => 1 + value_contents_eq(val, 4, val, 6, 2) => 1 + value_contents_eq(val, 0, val, 4, 4) => 0 + + We only know whether a value chunk is unavailable or optimized out + if we've tried to read it. As this routine is used by printing + routines, which may be printing values in the value history, long + after the inferior is gone, it works with const values. Therefore, + this routine must not be called with lazy values. */ + +extern int value_contents_eq (const struct value *val1, int offset1, + const struct value *val2, int offset2, + int length); /* Read LENGTH bytes of memory starting at MEMADDR into BUFFER, which is (or will be copied to) VAL's contents buffer offset by |