Summary:
This is several inter-connected changes together to keep the tests
happy.
The ConditionalOperator `b?t:e` is translated by first creating a
placeholder variable to temporarily store the result of the evaluation
in each branch, then the real thing we want to assign to reads that
variable. But, there are situations where that changes the semantics of
the expression, namely when the value created is a struct on the stack
(eg, a C++ temporary). This is because in SIL we cannot assign the
*address* of a program variable, only its contents, so by the time we're
out of the conditional operator we cannot set the struct value
correctly anymore: we can only set its content, which we did, but that
results in a "shifted" struct value that is one dereference away from
where it should be.
So a batch of changes concern `conditionalOperator_trans`:
- instead of systematically creating a temporary for the conditional,
use the `trans_state.var_exp_typ` provided from above if available
when translating `ConditionalOperator`
- don't even set anything if that variable was already initialized by
merely translating the branch expression, eg when it's a constructor
- fix long-standing TODO to propagate these initialization facts
accurately for ConditionalOperator (used by `init_expr_trans` to also
figure out if it should insert a store to the variable being
initialised or not)
The rest of the changes adapt some relevant other constructs to deal
with conditionalOperator properly now that it can set the current
variable itself, instead of storing stuff inside a temp variable. This
change was a problem because some constructs, eg a variable declaration,
will insert nodes that set up the variable before calling its
initialization, and now the initialization happens *before* that setup,
in the translation of the inner conditional operator, which naturally
creates nodes above the current one.
- add a generic helper to force a sequential order between two
translation results, forcing node creation if necessary
- use that in `init_expr_trans` and `cxxNewExpr_trans`
- adjust many places where `var_exp_typ` was incorrectly not reset when translating sub-expressions
The sequentiality business creates more nodes when used, and the
conditionalOperator business uses fewer temporary variables, so the
frontend results change quite a bit.
Note that biabduction tests were invaluable in debugging this. There
could be other constructs to adjust similarly to cxxNewExpr that were
not covered by the tests though.
Added tests in pulse that exercises the previous bug.
Reviewed By: da319
Differential Revision: D24796282
fbshipit-source-id: 0790c8d17
Summary:
As title.
This diff is co-authored by SungKeun Cho and me.
facebook
This diff is co-authored by skcho and me.
Original comments from skcho
"For the record:
1. Rory and I tried to write models for ObjC iterator.
2. We could not use Java's iterator semantics: In Java's, `hasNext` returns the size of collection, rather than a boolean, and which is used as a control variable. On the other hand, in ObjC, it calls only `nextObject`, not calling `hasNext`, and the return value of which is being checked as `null`.
3. We added an artificial field `objc_iterator_offset` to keep the index of the iterator, and the models added in this diff are handling that integer value.
A problem is that `array.objc_iterator_offset` is not included in the control variables, since the condition of the loop is `nextObject() != null` that does not include the iterator offset. We need to make `array.objc_iterator_offset` as a control variable, by changing the part collecting control variables.
"
Reviewed By: ezgicicek, skcho
Differential Revision: D22944278
fbshipit-source-id: 7e71b79c1
Summary:
As title
Model `NSString` as `JavaString`.
Since `NSArray` does not contain information about its type of element, we do not use associate string with collection as in Java and C++. In Java, String model is implemented using java collection, and for C++, string model is implemented using vector.
So instead, we use existing `JavaString` model.
Reviewed By: skcho
Differential Revision: D22431949
fbshipit-source-id: 7cdde1ad7
Summary:
Previous translation of enum constants were wrong since they assumed that the enum constant didn't include any global variable (hence they just looked up the enum exp from the map, forgetting to tie the respective instructions into the cfg).
```
const int gvar = 0;
enum {
evar = gvar,
};
int dangling() {
return evar;
}
```
as a result, the CFG was missing the instruction for the load of the `gvar`.
{F237004587}
This diff fixes this issue by hooking up the instructions that load the enum constant in to the CFG. Note that in this example, it is only a load instruction but there could be more instructions (e.g. if we had `gvar > 1`, we would have prune +join).
{F237004493}
Reviewed By: ezgicicek
Differential Revision: D21549781
fbshipit-source-id: 525534fb2
Summary:
This diff limits the depth of abstract location by a constant.
problem: Inferbo generated too many of abstract locations, especially when struct types had many pointer fields and Inferbo was not able to analyze the objects precisely. Since the number of generated abstract locations were exponential to the number of fields, it resulted in OOM in the end.
(reported by zyh1121 in https://github.com/facebook/infer/issues/1246)
Reviewed By: jvillard
Differential Revision: D20818471
fbshipit-source-id: f8af27e5c
Summary:
Current domain of Inferbo cannot handle float values. This diff evaluates float constants to the top
interval.
Reviewed By: ezgicicek
Differential Revision: D20116361
fbshipit-source-id: e6e398bbd
Summary:
Inferbo analyzed some program points unreachable incorrectly, because of unsound semantics of band
operator, which did not handle the case when given parameters are pointer values.
Reviewed By: ngorogiannis
Differential Revision: D19392705
fbshipit-source-id: dd590508c
Summary:
A plugin update allows infer to know when a function doesn't return
according to its attributes. This propagates this info all the way to
the attributes of each function, and then use this information in a new
pre-analysis that cuts the links to successor nodes of each `Call`
instruction to a function that does not return.
NOTE: The "no_return" `CallFlag.t` was dead code, following diffs deal
with that (by removing it).
Reviewed By: dulmarod
Differential Revision: D18573922
fbshipit-source-id: 85ec64eca
Summary:
This diff revises widening functions of bounds that have a linear form and a min/max form.
For example, for lower bounds,
* 3 ▽ (1+min(2, x)) = (1+min(2, x))
* 3+x ▽ (3+min(2, x)) = (3+min(2, x))
Reviewed By: jvillard
Differential Revision: D17420786
fbshipit-source-id: ff9eebed3
Summary:
This diff avoids that an integer value is pruned to the bottom by
comparing to a pointer.
For example, before this diff,
assume((int*)x == p);
assume((int*)x != p);
where x is an integer, x is pruned to the bottom in both of the assume
cases. So, there were some, unintentional and false, unreachable
code.
Depends on D16960199
Reviewed By: ezgicicek
Differential Revision: D16964735
fbshipit-source-id: 90a3c8c80
Summary: Sometimes programmers use integer underflow to get a maximum number of that type. This diff assumes that integer underflows from the syntactical form `(unsigned 0) - constant` is intended by the programmer, and suppresses the alarms of which.
Reviewed By: ezgicicek
Differential Revision: D16560639
fbshipit-source-id: 206f30dbc
Summary:
Before this diff, it gave up pruning of linear bound by minmax bound.
For example, `overapprox_min (x+c1, c2+min(d1,y))` was `x+c1`.
However, we can get a bit more preciser value as follows.
```
overapprox_min (x+c1, c2+min(d1,y))
<= min (x+c1, c2+d1)
= c1+min(c2+d1-c1, x)
```
Reviewed By: ezgicicek
Differential Revision: D16543837
fbshipit-source-id: 8fdbce097
Summary: This diff tries to do weak update for the abstract locations by pointer arithmetic, e.g. `p[n]` or `p+n`, even if the type of `p` is declared as a simple pointer, not an array.
Reviewed By: ezgicicek
Differential Revision: D16458367
fbshipit-source-id: 3b4cdd7e4
Summary:
Thanks to the newly added `StarField`, path length is better controlled before ondemand is used.
Hence there is no need to (unsoundly) canonicalize paths then anymore.
Reviewed By: ezgicicek
Differential Revision: D15409716
fbshipit-source-id: 9ea7b4717
Summary:
Some edge case involving casting field pointers to the structure type itself generated arbitrarily long paths when used in a loop.
Without changing the widening, this diff avoids repetitions of fields in paths by abstracting them with a star.
E.g. `x.a.b.c.b` will become `x.a.b.c*.b`, and so will `x.a.b.c.a.b`, `x.a.b.c.c.b`, or `x.a.b.c.b.b`.
Reviewed By: ngorogiannis
Differential Revision: D15352143
fbshipit-source-id: 5ea426c5e
Summary:
This diff propagates LatestPrune on function calls.
Depends on D14321605
Reviewed By: mbouaziz
Differential Revision: D14321618
fbshipit-source-id: cb2e1b547
Summary:
Given a pointer-typed parameter, Inferbo assumes that it is an array
block. However, when a pointer is given as an actual parameter, it
failed the substitution of the array block value of the parameter, thus
which made some return values to bottom unexpectedly.
This diff revises the substitution of array block, so it can
substitute array block values with actual pointers correctly when it
is possible.
Reviewed By: mbouaziz
Differential Revision: D14663475
fbshipit-source-id: 0477de1ba
Summary: Unknown locations in the alias domain resulted in unexpected unreachable code.
Reviewed By: mbouaziz
Differential Revision: D14339412
fbshipit-source-id: a5dca6489
Summary:
This diff differentiates proof obligations by allocsites. Sizes and
offsets of arrays were joined when making proof obligations.
Reviewed By: mbouaziz
Differential Revision: D14163149
fbshipit-source-id: cb6608c16
Summary:
This diff adds a constant to the set of widening thresholds if the
constant is compared to an abstract value in condition expressions.
Each abstract value has its own set of thresholds.
Reviewed By: mbouaziz
Differential Revision: D14147150
fbshipit-source-id: ca0db34d4
Summary:
In this diff, it avoids a precision-losing pruning, which was needed
to keep effects of assume commands.
```
unsigned int c = a + b; // (1)
if (c > 0) { // (2)
char result[c];
result[c - 1] = 0; // (4)
}
```
For example, in the example, `c` is assigned by `[a+b,a+b]` at (1),
then it tried to prune the lower bound of `c` to 1 at (2) while losing
precision, in order to say `c - 1` at (4) is safe in terms of integer
underflow. Instead, it could not say that `c - 1` is smaller than `c`
in the buffer access, because the former is analyzed to `[0,a+b-1]` and
the latter `[1,a+b]` at (4).
Now, the situation has changed. By adopting conditional proof
obligation (D13749914), the FP of integer overflow can be suppressed
without the precision-losing pruning.
Reviewed By: mbouaziz
Differential Revision: D14122770
fbshipit-source-id: 634744e99
Summary: Since Inferbo's current min/max domain can keep only a single symbol, e.g. min(constant, symbol) , it loses precision when trying to prune a value including multiple symbols.
Reviewed By: ezgicicek
Differential Revision: D14099399
fbshipit-source-id: 71d677b75
Summary: It keeps alias of simple plus/minus arithmetic in order to pruning the value of "++i" expression.
Reviewed By: mbouaziz
Differential Revision: D14080230
fbshipit-source-id: d3af32a32
Summary:
If the result of `fgets` is not-null, the length of `s` should be
bigger than or equal to 1.
Reviewed By: mbouaziz
Differential Revision: D13939994
fbshipit-source-id: 298fe33f4
Summary:
It adds a semantics for evaluation of abstract location of literal
string, which was missing.
Reviewed By: mbouaziz
Differential Revision: D13915265
fbshipit-source-id: 741df843b
Summary:
This diff extends the abstract domain to keep binary conditions on
prunings, so Inferbo can suppress more proof obligations (i.e., false
positives) that are known to be unreachable according to the binary
conditions.
Depends on D13729600
Reviewed By: mbouaziz
Differential Revision: D13749914
fbshipit-source-id: 314f048f1
Summary:
`memcpy` should copy the contents of the source to the destination.
Depends on D13634754
Reviewed By: ezgicicek, mbouaziz
Differential Revision: D13668414
fbshipit-source-id: cb0ff2010
Summary: It extends the abstract location for C string length, i.e., the first index of the null character in character array.
Reviewed By: mbouaziz
Differential Revision: D13634241
fbshipit-source-id: d2727d5f5
Summary:
This diff prevents deduplications of issues when they have different
conditions to reach.
Reviewed By: mbouaziz
Differential Revision: D13596220
fbshipit-source-id: 95f802edb
Summary: This diff unset powloc and arrayblk values of p when assume(p==Null).
Reviewed By: mbouaziz, jvillard
Differential Revision: D13415366
fbshipit-source-id: a491a957f
Summary:
For abstract values representing one concrete value, create only one symbol instead of two.
Still create two symbols (lb, ub) for abstract values representing multiple concrete values (like array cells).
As a consequence, comparisons of symbolic values are more precise (we can even prove equality). I expect to remove a bunch of FPs.
Another consequence is the disappearance of `.lb` and `.ub` in many reports.
Reviewed By: skcho
Differential Revision: D13072084
fbshipit-source-id: 9bc0b9881
Jules Villard
Qianyi Shu
Sungkeun Cho
Dulma Churchill
Josh Berdine
Mehdi Bouaziz