|
_Flaviu wrote: it is correct to write:
char* file_name[_MAX_PATH];
Yes, it is correct presuming you are going to define the array of pointers
|
|
|
|
|
Or
char* file_name[1];
? anyway, is more than 0 
|
|
|
|
|
Well, it all depends upon what you are going to achieve... 
|
|
|
|
|
_Flaviu wrote: Or
char* file_name[1];
Yes.
The only reason someone would declare zero-length is to dynamic allocate the array. You should change the array length to [1]. If you change it to _MAX_PATH (260) then you will be wasting 1036 bytes on a 32 bit machine and wasting 2072 bytes on a 64 bit machine.
Wasting bytes is punishable by death.
Best Wishes,
-David Delaune
modified 6-Aug-19 5:37am.
|
|
|
|
|
Quote: You should change the array length to [1]
Quote: Wasting bytes is punishable by death
Take your own conclusions. 
|
|
|
|
|
Hmmm,
The law states that wasting bytes less or equal to 1 * sizeof(pointer) is allowed but only in the month of August.
I guess he could remove the array qualifier but then that would probably break his compile.
Best Wishes,
-David Delaune
|
|
|
|
|
Disabling the warning is an option.
|
|
|
|
|
|
Thank you !
|
|
|
|
|
Quote: _MAX_PATH (260) then you will be wasting 236 bytes on a 32 bit machine and wasting 472 bytes on a 64 bit machine
Hey David, the math there is not clear to me. Do I need more caffeine this morning?
|
|
|
|
|
CPallini wrote: Do I need more caffeine this morning?
No, but I do...
Best Wishes,
-David Delaune
|
|
|
|
|
If you are on C11 ... C11 6.7.9/14 allows the option
char file_name[];
It was addedd for exactly that reason
In vino veritas
|
|
|
|
|
|
That is not a struct or a union. Is there some other code that you need to show us?
|
|
|
|
|
The original code is:
typedef struct {
....
....
char* file_name[0];
};
also, I get another warning here:
warning C4094: untagged 'struct' declared no symbols
I don't know how to get rid of this warnings ...
|
|
|
|
|
You are using a typedef but have not given it the name that you wish to use. It should be something like:
typedef struct {
....
....
char* file_name[0];
} myStruct;
Also the comment on the last line makes no sense; firstly it is declaring an aray of pointers rather than characters. And secondly, you should not store Unicode characters in a char type array. It will most likely cause problems at run time.
The zero length array is possibly valid, but it depends on how the code uses the struct. It can be used as a placeholder name for space that will be allocated for a dynamic structure at run time. Something like:
struct foo
{
int i;
char text[0];
};
struct foo* myFoo = (struct foo*)malloc(sizeof(struct foo) + 20);
|
|
|
|
|
I was about to write an answer when i saw this. Yes, zero length char arrays at the end of a struct appeared to be quite common in C programming some years (or decades, rather) ago. I haven't seen it in any C++ code ever, although it probably works the same. Whatever you wish to achieve, there's probably a better solution available in C++ syntax. Usually, std::string is the go to solution here.
That said, yes, it must be char [], not char* [], otherwise it doesn't make any sense at all.
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
|
|
|
|
|
Stefan_Lang wrote: it doesn't make any sense at all.
Sadly true of so much that we see here.
|
|
|
|
|
pretty sure you could just use char* name;
since the array size is 0.
|
|
|
|
|
Read carefully the documentation[^] (see the sample code).
Using _MAX_PATH (or whatever >0) is correct, the impact is in memory: each time the struct is allocated, _MAX_PATH character pointers are allocated too. You might instead choose to disable the warning, if it makes sense (e.g. there is an additional field in the struct specifying the actual size of the array).
|
|
|
|
|
I guess disabling this warning is best solution … how can I do that ? With pragma statement ? If yes, which version of pragma should I use ?
|
|
|
|
|
Never disable warnings, they are there to help you.
|
|
|
|
|
Don't disable warnings unless you are 100% sure what they're telling you, 100% sure that this is not a problem for the syntactic and semantic functionality of your code, and at least 90% sure there's no reasonable way to avoid them.
Under these conditions, the best way is to use #pragma push immediately before the disable command and #pragma pop after the code that causes the warning. That way you can be sure that the remainder of the code will use the same warning settings as defined in the compiler options.
GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)
|
|
|
|
|
Sorry, I didn't saw the link first time ...
modified 6-Aug-19 5:21am.
|
|
|
|
|
I am trying to integrate some old C code in a C++/MFC project and I met a strange error:
error C2143: syntax error : missing ')' before '{'
error C2059: syntax error : ')'
error C2143: syntax error : missing ')' before '{'
error C2143: syntax error : missing ')' before '{'
error C2143: syntax error : missing ';' before '{'
error C2059: syntax error : '{'
error C2059: syntax error : ')'
error C2059: syntax error : ')'
error C2059: syntax error : '=='
error C2059: syntax error : ')'
Here is the code:
static int some_function(const geometry_t* geometry)
{
if (struct_cmp(geometry->part_type, GEOM_TYPE_X) == 0) return 1;
return 0; }
Here is how is defined GEOM_TYPE_X:
#define GEOM_TYPE_X \
((const air_t){0, 0, 0, 0, 0, {0, 0, 0, 0, 0, 0}})
and air_t is:
typedef struct air_s air_t;
struct air_s
{
unsigned int val1;
unsigned short val2;
unsigned short val3;
unsigned char val4;
unsigned char val5;
unsigned char node[6];
};
geometry->part_type is the same air_t type ... and struct_cmp is:
static inline int struct_cmp(const air_t left, const air_t right)
{
return memcmp(&left, &right, sizeof(air_t));
}
Why I get this errors ? Where I should modify the code to make it run ? I have tried to modify GEOM_TYPE_X in several ways, no one has worked ...
Can you give me a little hint to get rid of this errors ?
P.S. Do you have enough information to see the problem ? If not, tell me to give you more details ...
modified 31-Jul-19 7:23am.
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
