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cfrontend/C2C.ml
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* Extend check for incomplete type.
Extended the check to also include a check for variables with
incomplete object type that are not arrays, that have an
initializer. Furthermore the warning includes the type and variable
name.
* Warning for incomplete type in compound literals.
Incomplete types are not allowed for compound literals, except for
array types.
* Extend type printing function.
The type of a typedeof of an anonymous type should not be printed.
Furthermore added '<anonymous>' to the printing of anonymous types.
* Unify incomplete type errors message.
The incomplete type error messages should all look the same including
name of the variable, parameter, etc. and then the incomplete type.
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The new diagnostics is triggered if a conditional is used that
may not be transformed into linear code by the later by the
if conversion.
The new diagnostic is emitted if a conditional may contain an
unsafe expression or is contained within another conditional,
logical and or logical or expression. An expression is unsafe if
it contains a call, changes memory or if its evaluation leads to
undefined behavior, for example division and modulo.
Also fixes a small typo in a comment in Cutil.
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The function determines whether the given type is an array type
or not.
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This commit adds a check to reject type definitions such as
```
typedef __attribute((section "foo")) int fooint;
```
GCC and Clang also reject this as an error.
Without the check, the behavior is somewhat surprising:
```
fooint x; // placed in section "foo"
fooint * x; // placed in default section, attribute "foo" is ignored
```
Note that the following must be accepted:
```
typedef struct { ... } __attribute((packed)) t;
```
The "packed" attribute is correctly attached to the struct type and should not be checked. This is achieved by using `attribute_of_type_no_expand` to get the attributes of the typedef-ed type, excluding the attributes carried by a struct/union or another typedef.
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This is a second step towards mimicking GCC/Clang's handling of attributes.
This commit introduces a distinction between
- Object-related attributes, such as "section", which apply to the object (function, variable) being defined;
- Name-related attributes, such as "aligned", which apply to the name (object, struct/union member, struct/union/enum tag) being defined.
In particular, "aligned" is now attached to "struct" and "union" definitions, while it used to be "floated up" before.
The C11 _Alignas modifier is treated like an object-related attribute, so that
```
struct s { ... };
_Alignas(64) struct s x;
```
correctly associates the alignment with "x" and not with "struct s", where it would be ignored because it was not part of the original definition of s.
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During elaboration of type declarators, non-type-related attributes such as "aligned" or "section" are "floated up" so that they apply to the thing being declared. For example, consider:
```
__attribute((aligned(16))) int * p;
```
The attribute is first attached to type `int`, then floated up to type `int *`, so that it finally applies to `p`, giving a 16-aligned pointer to int, and not a naturally-aligned pointer to 16-aligned int.
What happens when the non-type-related attribute comes from a typedef?
```
typedef __attribute((aligned(16))) int i16;
i16 * p;
```
CompCert used to expand the typedef then float up the attribute, resulting in `p` being a 16-aligned pointer to int.
GCC and Clang produce a naturally-aligned pointer, so they do not expand the typedef before floating.
The old CompCert behavior is somewhat surprising, and potentially less useful than the GCC/Clang behavior.
This commit changes the floating up of non-type-related attributes so that typedefs and struct/union/enum definitions are not expanded when determining which attributes to float up. This is a first step towards mimicking the GCC/Clang behavior.
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* Refactor common code of alignas.
Instead of working on attributes the function now works directly
on the type since the check always performed an extraction of
attributes from a type.
Bug 23393
* Attach _Alignas to the name.
Bug 23393
* Attach "aligned" attributes to names
So that __attribute((aligned(N))) remains consistent with _Alignas(N).
gcc and clang apply "aligned" attributes to names, with a special case
for typedefs:
typedef __attribute((aligned(16))) int int_al_16;
int_al_16 * p;
__attribute((aligned(16))) int * q;
For gcc, p is naturally-aligned pointer to 16-aligned int and
q is 16-aligned pointer to naturally-aligned int.
For CompCert with this commit, both p and q are 16-aligned pointers
to naturally-aligned int.
* Resurrect the alignment test involving typedef
The test was removed because it involved an _Alignas in a typedef,
which is no longer supported. However the same effect can be achieved
with an "aligned" attribute, which is still supported in typedef.
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The check tests whether the standard _Alignas is contained within
a given attribute list.
Bug 23391
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Restrict is only allowed for pointers whose referenced type is an
object type or incomplete type, but not a function type.
Bug 23397
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* Add diagnostic for type qualified arrays that occur in the wrong place
Arrays with type qualifiers (e.g. int t[const 5]) are only allowed as
function parameters and for them
only the outermost array type derivation.
Bug 23400
* Keep attributes from array for argument conversion
Type qualifiers of arrays in function parameters are just syntactic sugar
to allow adding them to the resulting pointer type. Hence, when a
qualified array type such as `int t[const 5]` decays into a pointer type
during argument conversion, the pointer type should be qualified, e.g. `int * const t`.
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* Error for structs with only flex array member
Flexible array members are only allowed if another member exists.
Bug 23324
* Added checks for nesting of structs with flex array members
Warn if a struct with a flex array member is used as array element
or member of another struct. Such usage is dubious.
Bug 23324
Don't warn if the struct-with-flex-array is a member of an union.
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CompCert has two implementations of sizeof, alignof and offsetof (byte offset of a struct field):
- the reference implementation, in Coq, from cfrontend/Ctypes.v
- the implementation used during elaboration, in OCaml, from cparser/Cutil.ml
The reference Coq implementation is used as much as possible, but sometimes during elaboration the size of a type must be computed (e.g. to compute array sizes), or the offset of a field (e.g. to evaluate __builtin_offsetof), in which case the OCaml implementation is used.
This causes issues with packed structs. Currently, the cparser/Cutil.ml functions ignore the "packed" attribute on structs. Their results disagree with the "true" sizes, alignments and offsets computed by the cfrontend/Ctypes.v functions after source-to-source transformation of packed structs as done in cparser/PackedStruct.ml. For example:
```
struct __packed__(1) s { char c; short s; int i; };
assert (__builtin_offsetof(struct s, i) == 3);
assert (sizeof(struct s) = sizeof(char[sizeof(struct s)]));
```
The two assertions fail. In the first assertion, __builtin_offsetof is elaborated to 4, because the packed attribute is ignored during elaboration. In the second assertion, the type `char[sizeof(struct s)]` is elaborated to `char[8]`, again because the packed attribute is ignored during elaboration, while the other `sizeof(struct s)` is computed as 7 after the source-to-source transformation of packed structs.
This commit changes the cparser/Cutil.ml functions so that they take the packed attribute into account when computing sizeof, alignof, offsetof, and struct_layout.
Related changes:
* cparser/Cutil: add `packing_parameters` function to extract packing info from attributes
* cparser/Cutil: refactor and share more code between sizeof_struct, offsetof, and struct_layout
* cparser/Elab: check the alignment parameters given in packed attributes. (The check was previously done in cparser/PackedStruct.ml but now it would come too late.)
* cparser/Elab: refactor the checking of alignment parameters between _Alignas, attribute((aligned)), __packed__, and attribute((packed)).
* cparser/PackedStructs: simplify the code, some functionality was moved to cparser/Cutil, other to cparser/Elab
* cfrontend/C2C: raise an "unsupported" error if a packed struct is defined and -fpacked-structs is not given. Before, the packed attribute would be silently ignored, but now doing so would cause inconsistencies between cfrontend/ and cparser/.
* test/regression/packedstruct1.c: add tests to compare the sizes and the offsets produced by the elaborator with those obtained after elaboration.
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Sizeof and _Alignof are not allowed on bit-fields
Sizeof and _Alignof are not allowed to be applied to a expression
that designates a bit-field member.
Bug 23311
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The ais annotations are now handled in a separate file shared
between all architectures. Also two different variants of
replacements are supported, %e which expands to ais expressions
and %l which also expands to an ais expression but is guaranted to
be usable as l-value in the ais annotation. Otherwise the new
warning is Wrong_is_parameter is generated.
Also an error message is generated if floating point variables are
used in ais annotations since a3 does not support them at the
moment.
Additionally an error message is generated for plain volatile
variables used, since they will enforce a volatile load and result
in the value being passed to the annotation instead of the address
as other global variables.
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The check tests whether the size calculation of an array overflows
or the array covers half of the available address space and reports
an error in this case.
Bug 21034
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The C11 standard declares exit,abort,_Exit,quick_exit and
thrd_exit as _Noreturn however this is not included in older C
libs and leads to false negatives in reporting _Noreturn and
return type warnings. This can be avoided by enhancing the
noreturn check of the Cflow analysis to also test if one of the
above functions is called.
Bug 21009
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Improved warnings related to function returns
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This commit introduces a control-flow static analysis over C abstract syntax (file cparser/Cflow.ml) and uses it to
- warn for non-void functions that can return by falling through the body
- warn more precisely for _Noreturn functions that can return
- introduce the "return 0" in "main" functions less often (cosmetic).
For the control-flow analysis, the following conservative approximations are made:
- any "goto" label is reachable
- all cases of a "switch" statement are reachable as soon as the "switch" is reachable (i.e. the switch expression takes all values needed to reach every case)
- the boolean expressions in "if", "while", "do"-"while" and "for" can take true and false values, unless they are compile-time constants.
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The optional hex parameter only worked if the intconstant was also
of unsigned kind. Hence it is better to have one function in
Bitfields for this.
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Introduce Cutil.class_of_attribute to return the class of the given attribute: one among
Attr_type attribute related to types (e.g. "aligned")
Attr_struct attribute related to struct/union/enum types (e.g. "packed")
Attr_function attribute related to function types (e.g. "noreturn")
Attr_name attribute related to variable and function declarations (e.g. "section")
Attr_unknown attribute was not declared
Cutil.declare_attribute is used to associate a class to a custom attribute.
Standard attributes (const, volatile, _Alignas, etc) are Attr_type.
cfronted/C2C.ml: declare the few attributes that CompCert honors currently.
cparser/GCC.ml: a bigger list of attributes taken from GCC, for reference only.
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The treatment of attributes in the current CompCert is often surprising. For example,
attribute(xxx) char * x;
is parsed as "x is a pointer to a (char modified by attribute "xxx")", while for most attributes (e.g. section attributes) the expected meaning is "x, modified by attribute "xxx", has type pointer to char".
CompCert's current treatment comes from the fact that attributes are processed very much like the standard type modifiers `const` and `volatile`, i.e.
const char * x;
is really "x is a pointer to a const char", not "x is a const pointer to char".
This experiment introduces a distinction between type-related attributes (which include the standard modifiers `const` and `volatile`) and other attributes. The other, non-type-related attributes are "floated up" during elaboration so that they apply to the variable or function being declared or defined. In the examples above,
attribute(xxx) char * x; // "attribute(xxx)" applies to "x"
const char * x; // "const" applies to "char"
This may be a step in the right direction but is not the final story. In particular, the `packed` attribute is special-cased when applied to `struct`, like it was before, and future attributes concerning calling conventions would need to be floated up to function types but not higher than that.
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The intconst function comes with an optional parameter to add an
hex string for later printing.
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Instead of multiplying the array constant directly with the
size of the offset the cautious_mul function is used to detect
potential overflows.
Bug 20765
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The c standard allows member designators for offsetof. The current
implementation works by recursively combining the offset of each
of the member designators. For array access the size of the
subtypes is multiplied by the index and for members the offset of
the member is calculated.
Bug 20765
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The implementation of offsetof as macro in the form
((size_t) &((ty*) NULL)->member) has the problem that it cannot be
used everywhere were an integer constant expression is allowed,
for example in initiliazers of global variables and there is also
no check for the case that member is of bitifield type.
The new implementation adds a builtin function for this which is
replaced by an integer constant during elaboration.
Bug 20765
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The warning missing declarations is now also triggered for
declarations without name in field lists of composite types if
the declaration is not an anonymous composite or a bitfield member.
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Since some incomplete types are allowed in initialization just
test whether the default initilization exists.
Bug 19601
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Now each warning either has a name and can be turned on/off, made
into an error,etc. or is a warning that always will be triggered.
The message of the warnings are similar to the ones emited by
gcc/clang and all fit into one line.
Furthermore the diagnostics are now colored if colored output is
available.
Bug 18004
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CompCert now recognizes the C11 _Noreturn function specifier and
emits a simple warning for functions declared _Noreturn containing
a return statement. Also the stdnoreturn header and additionally
the stdalign header are added.
Bug 18541
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Removed some unused variables, functions etc. and resolved some
problems which occur if all warnings except 3,4,9 and 29 are active.
Bug 18394.
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Debug statements introduced during the translation result in warnings
when they are introduced at the head of the switch. Since they are
not used and the warning is not necessary we can remove them before.
Fix 17580.
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Since the strip functions might be useful in other context and is
more general then the debug information.
Bug 17392.
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C11 allows a typedef redefinition if the types are the same.
We now allow this also and issue a warning and an error if the types are different.
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Added functions to add more information to the debuging interface,
like the struct layout with offsets, bitifiled layout and removed
the no longer needed mapping from stamp to atom.
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bit field.
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Conflicts:
Makefile
driver/Driver.ml
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The passing of struct/union arguments by value implemented in the verified
part of CompCert is not compatible with the ARM, PowerPC and x86 ABI.
Here we enrich the StructReturn source-to-source emulation pass
so that it implements the calling conventions defined in these ABIs.
Plus: for x86, implement the returning of struct/union results by value
in a way compatible with the ABI.
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- Switch CompCert C / Clight AST of composite types (structs and unions)
from a structural representation to a nominal representation,
closer to concrete syntax.
- This avoids algorithmic inefficiencies due to the structural representation.
- Closes PR#4.
- Smallstep: make small-step semantics more polymorphic in the type of the
global environment.
- Globalenvs: introduce Senv.t (symbol environments) as a restricted view
on Genv.t (full global environments).
- Events, Smallstep: use Senv instead of Genv to talk about global names.
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Use these constructor functions in C2C to rely less on the types produced
by the unverified elaborator.
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Several definitions in Cutil and elsewhere were accessing the default
value of !Machine.config, before it is properly initialized in Driver.
Delay evaluation of these definitions, and initialize Machine.config
to nonsensical values so that lack of initialization is caught early
(e.g. in Cutil.find_matching_*_kind).
Also, following up on commit [3b8a094], don't use "wchar_t" typedef
to type wide string literals, even if this typedef is in scope.
The risk here is to hide an inconsistency between "wchar_t"'s definition
in standard headers and CompCert's built-in definition.
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We now distinguish 3 modes (instead of 2 previously) for attributes: 1- strict compatibility, 2- ignore top-level attrs, 3- ignore all attrs recursively.
In strict mode, const/volatile/restrict attributes must be identical, but nonstandard attributes may vary.
Also: ignore top-level attrs when comparing function argument types, like GCC/Clang do.
Net result is fewer warnings and type-checking that is closer to GCC/Clang.
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- cparser/Machine indicates whether wchar_t is signed or not
(it is signed int in Linux and BSD, but unsigned short in Win32)
- The type of a wide string literal is "wchar_t *" if the typedef "wchar_t"
exists in the environment (e.g. after #include <stddef.h>). Only if
wchar_t is not defined do we use the default from Machine.
- Permit initialization of any integer array from a wide string literal,
not just an array of wchar_t.
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- Ctypes: add useful functions on attributes; remove attrs in typeconv
(because attributes are meaningless on r-values)
- C2C: fixed missing or redundant Evalof
- Cop: ignore attributes in ptr + int and ptr - int (meaningless on r-values);
add sanity check between typeconv/classify_binarith and the C99 standard.
- cparser: fixed several cases where incorrect type annotations were put
on expressions.
git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@2457 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
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