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Questions tagged [gcc-attribute]

7 questions
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What preprocessor condition should I check so as to use __attribute__((const))?

I've gotten a piece of code which applies __attribute__((const)) to some functions. Now, I'd rather not remove it when it's usable, but on the other hand, I do want to be more portable, so - I want to say #if some condition here #define…
einpoklum
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What does "mode" attribute do?

I have read the documentation but I am not able to understand it. What does following typedefs do? What is/should be size of a variable of type word/pointer/_Unwind_Word on a 8/16/32/64 bit architecture? typedef unsigned int word…
jdx
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__attribute__ in definitions of multiple variables

I have a question which is best explained by example. Please consider the following code: unsigned char a, b; This obviously defines two variables of type unsigned char. If I would like to make the variables aligned to…
Binarus
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How can I create a platform-independent macro to wrap a compiler extension?

I have some code like this that I need to make cross-platform: int __attribute__((noinline)) fn() { return 0; } I want to use Waf to write a config.h that contains #define ATTRIBUTE(attr) __attribute__((attr)) if the compiler supports this…
user2201041
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why weak attribute has not been selected for C23?

I can see that there is a new keyword type 'attributes' in C23. Some of it, like [[deprecated]] were used in C11+GNU __attribute__((deprecated)). I looks like a great update. I wonder why a usefull keyword as __attribute__((weak)) is not part of the…
Guillaume D
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GCC attribute __attribute__ ((constructor)) from main executable runs after linked libraries constructors

I noticed that constructors from shared objects linked into my applications will always run before my application constructors, even if my applications has lower priority number (ie: higher priority); for example, let's say this program: #include…
Federico
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Is a C struct of all-packed fields except first one different from packed struct?

Among its Common Type Attributes, GCC provides packed: This attribute, attached to a struct [...] type definition, specifies that each of its members (other than zero-width bit-fields) is placed to minimize the memory required. This is equivalent…
PiCTo
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