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Questions tagged [function-attributes]

36 questions
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1 answer

Explain force_align_arg_pointer function attribute

From the GCC documentation On the Intel x86, the force_align_arg_pointer attribute may be applied to individual function definitions, generating an alternate prologue and epilogue that realigns the runtime stack. This supports mixing legacy codes…
manav m-n
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Is it possible to declare the function's attribute outside of where it is defined? (GCC)

In GCC, many function attributes can be used to give syntax to the compiler for useful optimization/profiling of the code. Helpful link: https://www.acrc.bris.ac.uk/acrc/RedHat/rhel-gcc-en-4/function-attributes.html For instance, the typical usage…
Jay
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Forcing a function to be optimized on clang or prologueless non-naked C functions - paste together blocks of asm based on C constants

Is there anyway to force a C function on clang to be optimized even when the file is compiled with -O0? I'm looking for something equivalent to gcc's __attribute((optimize("s")) or __attribute((optimize(3)). (Related: In clang, how do you use…
Petr Skocik
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Does asmlinkage mean stack or registers?

In most languages, C included, the stack is used for function calls. That's why you get a "Stack Overflow" error if you are not careful in recursion. (Pun not intended). If that is true, then what is so special about the asmlinkage GCC directive. It…
ng.newbie
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Why is no warning given for the wrong use of __attribute__((pure)) in GCC?

I am trying to understand pure functions, and have been reading through the Wikipedia article on that topic. I wrote the minimal sample program as follows: #include static int a = 1; static __attribute__((pure)) int pure_function(int x,…
Abhishek Chakravarti
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Optimization problem with [[gnu::pure]] function attribute and threads

I have a program which nearly immediately finishes with -O0 on gcc, but hangs forever with gcc and -O3. It also exits immediately if I remove the [[gnu::pure]] function attribute, even though the function does not modify global state. The program is…
Omnifarious
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using function attributes to store results for lazy (potential) processing

I'm doing some collision detection and I would very much like to use the same function in two different contexts. In one context, I would like for it to be something like def detect_collisions(item, others): return any(collides(item, other) for…
aaronasterling
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LLVM how to set Attributes::NoUnwind to Function?

I think this is very simple question, but I can't resolve it. Very sad. So. When I do llc.exe -march=cpp test.bc I get interesting test.cpp with this piece of code: AttrListPtr func__Z2f1i_PAL; { SmallVector Attrs; …
kpdev
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gcc 12 suggesting to add the "pure" attribute

I have written a container class very similar to std::vector. It has a size() member function, which I declared noexcept, const and constexpr. class my_vector { ... constexpr auto size() const noexcept -> size_type { assert(stride_…
alfC
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Is function declared as __attribute__ ((pure)) allowed to return newly constructed std::string

In gnu world of C/C++ with GCC compiler there is Common function attribute "pure" (which is like "const" attribute, but with less restrictions): Many functions have no effects except the return value and their return value depends only on the…
osgx
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Is it possible to have a make a generic method which can take the place of three methods with a System.Data.Linq.Mapping.FunctionAttribute?

I have three methods in my datacontext class which all call slightly different stored procedures having different behaviours; APPEND, UPDATE, OVERWRITE. However all three methods have in essence the same code. The only difference is the "Name"…
Dib
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How to mark a function with return type not to return?

If I don't return anything in a function which returns something, compiler will warn about the function is not returning anything. But If I call abort() in the function, compiler won't warn. How can I mark my own function like this.
eonil
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In Python, how can I use a function attribute as a function?

In Python, you could define a function attribute "call_count" such that: def counter(func): def inner(*args): inner.call_count+= 1 return func(*args) inner.call_count= 0 return inner def sum(a, b, c): return…
Charlie Brown
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Mark function to be used only under lock

I'm writing a linux kernel driver and I have a function which MUST be called under lock, and I want to make sure no one will use it without acquiring the lock. This function is called many times from different functions which acquire the lock prior…
Idan Emergi
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Python scipy.optimize.f_min_l_bfgs_b algorithm: how to have extra outputs?

I am using L-BFGS-B optimizer from Scipy package. Here is the documentation. My code has the following structure. obj_func is the objective function that is used to minimize "a". In order to do so, obj_func should only return "a". Question: Is…
zcadqe
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