Packing class or struct to place its members directly after each other in memory, which can mean that some or all members can be aligned on a boundary smaller than the default alignment the target architecture
Questions tagged [pragma-pack]
29 questions
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3 answers
What is `#pragma pack` for in network programming?
#pragma pack(push)
#pragma pack(1)
I downloaded a tutorial and it has these lines in the header file.
I will appreciate if you guys can provide me any tutorials or references related to this.
codereviewanskquestions
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1 answer
wcslen() returns incorrect result when pragma pack used
I've found that wcslen() returns incorrect result on gcc(and correct on msvc) when source is wchar_t array, member of packed struct. I know on linux sizeof(wchar_t) == 4 and on windows its 2 but still can't understand how packing affects wcslen()…
Alex
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2 answers
Copying a struct into a byte array
I have a 1-byte pragma packed struct in C which I want to copy into a byte array for serialization purpose to be sent over a serial port.
#pragma pack(push, 1)
typedef struct {
uint8_t ck_a;
uint8_t ck_b;
} UBXChecksum_t ;
#pragma…
Akay
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1 answer
Compile time check for usage of #pragma pack
Most compiliers support changing the packing of a class by using a #pragma pack(N) directive, where N is the new minimum acceptable alignment for each member.
Is it possible to check at compile-time whether or not a #pragma pack(N) has been…
Adam Yaxley
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1 answer
passing address of packed struct member
I am developing a C/C++ application where in I am using packed struct members. I have read that we should never pass address of packed struct members to any function(I always used to get alignment errors when passing packed struct members by…
Harry
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pragma pack(n) vs pragma pack(push,n)
What is the difference between
pragma pack(n) and pragma pack(push,n)
#pragma pack(pop) and #pragma pack()
Can someone explain through an example ? Which should be used when ?
I went through…
Cool Camel
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1 answer
What is the effect of #pragma pack() when it follows a struct definition?
I have read other posts as well as the Microsoft Docs regarding the effect of #pragma pack(). I understand that it is useful when byte alignment is necessary.
However, I am still unsure of the effect of putting #pragma pack() both before and after…
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0 answers
Forgot pragma pack(pop) program crashes
#pragma pack(push, 1)
typedef enum __attribute__ ((__packed__)) {
ETypeZero = 0,
ETypeOne,
ETypeTwo,
ETypeUndefined
} ESomeType;
#pragma pack(pop)
In my code above, I had accidentally forgot #pragma pack(pop), and I saw some other…
Nishikant
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0
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1 answer
How to align a structure correctly?
I am trying to align a structure using the directive (#pragma pack).
I need it has 112 bytes in size. (14*8=112 bytes).
However it has 80 bytes only.
How to do it correctly?
#pragma pack (8)
struct Deal
{
long deal_ticket;
long …
Iván Rodríguez
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2 answers
C macro for inlining functions with IAR compiler
With previous gcc compiler we did this:
#define DO_PRAGMA(x) _Pragma(#x)
#define PACK_ON(n) DO_PRAGMA(pack(n))
so in effect would mean PACK_ON(2) would expand to be _Pragma(pack(2))
Then we would use it like this
PACK_ON(2)
typedef…
Adeishere
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0
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1 answer
Byte layout of structure (#pragma pack behavior) different on MSVC vs clang/gcc
The following code generates a different layout in memory on MSVC vs clang/gcc. Why?
#include
#pragma pack(push,1)
struct empty_struct
{
};
class derived_struct : public empty_struct
{
int m_derivedMember;
};
class…
Phenglei Kai
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0
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1 answer
#pragma pack(1) causes segmentation fault
At some point my big project's code started getting segmentation fault runtime errors with such stacktrace:
0# std::basic_ios >::widen (__c=10 '\n', this=) at /usr/include/c++/7/bits/basic_ios.h:450
1# std::endl > (__os=...) at…
Slaus
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2 answers
Is `#pragma pack(1)` risky/dangerous if a struct contains only byte arrays
Is it dangerous/risky to use #pragma pack(1) on structs that contain byte-arrays only? E.g. this one:
#pragma pack(1)
struct RpcMessage {
uint8_t proto_info[16];
uint8_t message_uuid[16];
uint8_t arg0[16];
uint8_t arg1[16];
…
K. Biermann
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C - Why #pragma pack(1) Consider 6-bit struct member as an 8-bit?
I got stuck about #pragma pack(1) wrong behavior when define a 6-bit field and assumes it as 8-bit. I read this question to solving my problem but it doesn't help me at all.
In Visual Studio 2012 I defined bellow struct for saving Base64 characters…
BattleTested_закалённый в бою
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