Recent work on -Wunreachable-code has focused on suppressing uninteresting
unreachable code that center around "configuration values", but
there are still some set of cases that are sometimes interesting
or uninteresting depending on the codebase. For example, a dead
"break" statement may not be interesting for a particular codebase,
potentially because it is auto-generated or simply because code
is written defensively.
To address these workflow differences, -Wunreachable-code is now
broken into several diagnostic groups:
-Wunreachable-code: intended to be a reasonable "default" for
most users.
and then other groups that turn on more aggressive checking:
-Wunreachable-code-break: warn about dead break statements
-Wunreachable-code-trivial-return: warn about dead return statements
that return "trivial" values (e.g., return 0). Other return
statements that return non-trivial values are still reported
under -Wunreachable-code (this is an area subject to more refinement).
-Wunreachable-code-aggressive: supergroup that enables all these
groups.
The goal is to eventually make -Wunreachable-code good enough to
either be in -Wall or on-by-default, thus finessing these warnings
into different groups helps achieve maximum signal for more users.
TODO: the tests need to be updated to reflect this extra control
via diagnostic flags.
llvm-svn: 203994
This warning has a whole bunch of known false positives, much of them due
to code that is "sometimes unreachable". This can caused by code that
is conditionally generated by the preprocessor, branches that are defined
in terms of architecture-specific details (e.g., the size of a type), and
so on. While these are all good things to address one by one, the reality
is that this warning has received little love lately. By restricting
its purvue, we can focus on the top issues effecting main files, which
should be smaller, and then gradually widen the scope.
llvm-svn: 201607
A return type is the declared or deduced part of the function type specified in
the declaration.
A result type is the (potentially adjusted) type of the value of an expression
that calls the function.
Rule of thumb:
* Declarations have return types and parameters.
* Expressions have result types and arguments.
llvm-svn: 200082
In an expression like "new (a, b) Foo(x, y)", two things happen:
- Memory is allocated by calling a function named 'operator new'.
- The memory is initialized using the constructor for 'Foo'.
Currently the analyzer only models the second event, though it has special
cases for both the default and placement forms of operator new. This patch
is the first step towards properly modeling both events: it changes the CFG
so that the above expression now generates the following elements.
1. a
2. b
3. (CFGNewAllocator)
4. x
5. y
6. Foo::Foo
The analyzer currently ignores the CFGNewAllocator element, but the next
step is to treat that as a call like any other.
The CFGNewAllocator element is not added to the CFG for analysis-based
warnings, since none of them take advantage of it yet.
llvm-svn: 199123
This new warning detects when a function will recursively call itself on every
code path though that function. This catches simple recursive cases such as:
void foo() {
foo();
}
As well as more complex functions like:
void bar() {
if (test()) {
bar();
return;
} else {
bar();
}
return;
}
This warning uses the CFG. As with other CFG-based warnings, this is off
by default. Due to false positives, this warning is also disabled for
templated functions.
llvm-svn: 197853
to be treated as return values, and marked with the "returned_typestate"
attribute. Patch by chris.wailes@gmail.com; reviewed by delesley@google.com.
llvm-svn: 192932
marked all variables as "unknown" at the start of a loop. The new version
keeps the initial state of variables unchanged, but issues a warning if the
state at the end of the loop is different from the state at the beginning.
This patch will eventually be replaced with a more precise analysis.
Initial patch by chris.wailes@gmail.com. Reviewed and edited by
delesley@google.com.
llvm-svn: 192314
that a function can be called in. This reduced the total number of annotations
needed and makes writing more complicated behaviour less burdensome.
Patch by chriswails@gmail.com.
llvm-svn: 191983
_Bool in C, if the macro is defined. Also teach FixItUtils to look at whether
the macro was defined at the source location for which it is creating a fixit,
rather than looking at whether it's defined *now*. This is especially relevant
for analysis-based warnings which are delayed until end of TU.
llvm-svn: 191057
variable uninitialized every time we reach its (reachable) declaration, or
every time we call the surrounding function, promote the warning from
-Wmaybe-uninitialized to -Wsometimes-uninitialized.
This is still slightly weaker than desired: we should, in general, warn
if a use is uninitialized the first time it is evaluated.
llvm-svn: 190623
Patch by chris.wailes@gmail.com
Functions can now declare what state the consumable type the are returning will
be in. This is then used on the caller side and checked on the callee side.
Constructors now use this attribute instead of the 'consumes' attribute.
llvm-svn: 189843
Patch by chris.wailes@gmail.com. The following functionality was added:
* The same functionality is now supported for both CXXOperatorCallExprs and CXXMemberCallExprs.
* Factored out some code in StmtVisitor.
* Removed variables from the state map when their destructors are encountered.
* Started adding documentation for the consumed analysis attributes.
llvm-svn: 189059
Reviewed by delesley, dblaikie.
Add the annotations and code needed to support a basic 'consumed' analysis.
Summary:
This new analysis is based on academic literature on linear types. It tracks
the state of a value, either as unconsumed, consumed, or unknown. Methods are
then annotated as CallableWhenUnconsumed, and when an annotated method is
called while the value is in the 'consumed' state a warning is issued. A value
may be tested in the conditional statement of an if-statement; when this occurs
we know the state of the value in the different branches, and this information
is added to our analysis. The code is still highly experimental, and the names
of annotations or the algorithm may be subject to change.
llvm-svn: 188206
Use Optional<CFG*> where invalid states were needed previously. In the one case
where that's not possible (beginAutomaticObjDtorsInsert) just use a dummy
CFGAutomaticObjDtor.
Thanks for the help from Jordan Rose & discussion/feedback from Ted Kremenek
and Doug Gregor.
Post commit code review feedback on r175796 by Ted Kremenek.
llvm-svn: 175938
Summary:
-Wimplicit-fallthrough: fixed two cases where "fallthrough annotation in unreachable code" was issued incorrectly:
1. In actual unreachable code, but not immediately on a fall-through execution
path "fallthrough annotation does not directly precede switch label" is better;
2. After default: in a switch with covered enum cases. Actually, these shouldn't
be treated as unreachable code for our purpose.
Reviewers: rsmith
Reviewed By: rsmith
CC: cfe-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D374
llvm-svn: 174575
it apart from [[gnu::noreturn]] / __attribute__((noreturn)), since their
semantics are not equivalent (for instance, we treat [[gnu::noreturn]] as
affecting the function type, whereas [[noreturn]] does not).
llvm-svn: 172691
with -Werror. Previously, compiling with -Werror would emit only the first
warning in a compilation unit, because clang assumes that once an error occurs,
further analysis is unlikely to return valid results. However, warnings that
have been upgraded to errors should not be treated as "errors" in this sense.
llvm-svn: 169649
As the analysis improves, it will continue to add new warnings that are
potentially disruptive to existing users. From now on, such warnings will
first be introduced under the "beta" flag. Such warnings are not turned on by
default; their purpose is to allow users to test their code against future
planned changes, before those changes are actually made. After a suitable
migration period, beta warnings will be folded into the standard
-Wthread-safety.
llvm-svn: 169338
uncovered.
This required manually correcting all of the incorrect main-module
headers I could find, and running the new llvm/utils/sort_includes.py
script over the files.
I also manually added quite a few missing headers that were uncovered by
shuffling the order or moving headers up to be main-module-headers.
llvm-svn: 169237
There was enough consensus that we *can* get a good language solution
to have an annotation outside of C++11, and without this annotation
this warning doesn't quite mean's completeness criteria for this
kind of warning. For now, restrict this warning to C++11 (where an
annotation exists), and make this the behavior for the LLVM 3.2 release.
Afterwards, we will hammer out a language solution that we are all
happy with.
llvm-svn: 167749
The rationale is that there is no good workflow to silence the warning
for specific cases, other than using pragmas. This is because the
attribute to decorate an explicit fall through is only available
in C++11.
By that argument, this should probably also be disabled unless one
is using C++11, but apparently there is an explicit test case for
this warning when using C++98. This will require further discussion
on cfe-commits.
Fixes: <rdar://problem/12584746>
llvm-svn: 167655
Previously, the warning would erroneously fire on this:
for (Test *a in someArray)
use(a.weakProp);
...because it looks like the same property is being accessed over and over.
However, clearly this is not the case. We now ignore loops like this for
local variables, but continue to warn if the base object is a parameter,
global variable, or instance variable, on the assumption that these are
not repeatedly usually assigned to within loops.
Additionally, do-while loops where the condition is 'false' are not really
loops at all; usually they're just used for semicolon-swallowing macros or
using "break" like "goto".
<rdar://problem/12578785&12578849>
llvm-svn: 166942
This is a "safe" pattern, or at least one that cannot be helped by using
a strong local variable. However, if the single read is within a loop,
it should /always/ be treated as potentially dangerous.
<rdar://problem/12437490>
llvm-svn: 165719
Ted Kremenek