| Commit message (Collapse) | Author | Age | Files | Lines |
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The check test whether the identifier is used at all in the
function and if not issue a warning. It is not tested whether the
usage is reachable at all, so
int i;
if (0)
i;
would not generate a warning. This is the same as gcc/clang does.
The warning is disabled per default, but is active if -Wall is
given.
Bug 19872
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As a cosmetic optimization enabled by the static analysis in Cflow, we used to not insert a 'return 0' at end of 'main' if the body of 'main' cannot fall through.
Since this optimization is cosmetic (the back-end will remove the 'return 0' if unused) and since we don't fully trust this static analysis, revert this optimization and always insert 'return 0'.
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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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Minor performance tweak. Printf is more efficient for plain formats involving no boxes.
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- Mark the "noreturn" attribute as related to function types, so that it is correctly attached to the nearest enclosing function type.
- Add this attribute on functions declared / defined _Noreturn (with the C2011 keyword). The information is not used presently but could be useful later.
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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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Owing to the peculiarities of array types in Cutil.change_attributes_type, type-related attributes of the array element type were duplicated on the array type. E.g. elaborating 'const int a[10][5]' produced
"a is an array of 5 const arrays of 10 const ints"
instead of
"a is an array of 5 arrays of 10 const ints"
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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 Cabshelper is only used in 4 places, so we don't need a global
open. Furhtermore the String.t type is now inlined for Cabs to
avoid shadowing problems in Elab.ml
Bug 19872
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Format was only used in one place without explicit module prefix.
The same holds for Env.
Bug 19872
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Since anonymous struct members are kept in the fieldlist, the
fieldlist can never be empty in this case.
Bug 19872
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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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Gcc and clang do not raise an error for this, also it should work
for the last array element which can be without size.
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 problem was that sub structs are were not correctly aligned.
The new version is much simpler and uses the sizeof_struct to
calculate the individual offsets and add them up to get correct
offest.
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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"try ...; true with _ -> false" is dangerous if "..." raises unexpected exceptions such as Out_of_memory or Stack_overflow.
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The naming of anonymous structs is performed by an additional step
in elab_struct_or_union_info instead of in elab_field_group.
Also the aux functions are renamed to access.
Bug 20003
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Instead of using idents the anonymous fileds get names of the
for <anon>_c where c is a counter of all anonymous members.
Bug 20003
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The warning for C11 features is now also triggered for _Noreturn.
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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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The anonymous members are kept but using them is still an error.
Bug 19907
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Now "expected at least %d" instead of "expected %d". Also improved
error message for __builtin_debug.
Bug 19872
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The only case where compcert raise a pedantic warning was for
implicit int parameters. This is the behavior of clang. However
since not all other pedantic warnings are supported the behavior
of gcc is adopted.
Bug 19872.
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In order to empty declarations it is necessary to distinguish
between forward declarations and empty declarations.
Bug 19859
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Now the same warning is triggered for both cases, int to ptr and
ptr to int.
Bug 18004
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This warning should be triggered if a feature is used that is not
part of the code CompCert C language.
Bug 18004
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Some old errors/warnings messages were better before and are now
rephrased. Furthermore some formulations are rephrased to match the
used formulations of the ISO C stanard, e.g. storage class is
replaced with storage-class.
Bug 18004
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The environment where the types are inserted is passed back to
allow introducing structs in k&r parameters.
Bug 19668
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The previous fix for duplicated members was also triggered for
unnamed members.
Bug 19665
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