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POmemcpy copying the wrong number of bytes
primarykey
Id
20820993
data
AcceptedAnswerId
20821320
AnswerCount
2
ClosedDate
CommentCount
15
CommunityOwnedDate
CreationDate
2013-12-29T00:45:29.400
FavoriteCount
0
LastActivityDate
2013-12-29T03:36:00.240
LastEditDate
2013-12-29T03:36:00.240
LastEditorUserId
2756220
OwnerUserId
2756220
ParentId
0
PostTypeId
1
Score
0
ViewCount
758
LastEditorDisplayName
text
Body
1.I have the following structure. <pre><code>typedef struct { unsigned int ibaseRecord; unsigned int irecordNumber; unsigned char brecordType; unsigned char brevision; unsigned int ipageNumber; unsigned int ireserve1; unsigned int ireserve2; unsigned int ireserve3; unsigned short scrc16; } DATABASEPAGEHEADER_TypeDef; </code></pre> I also have following byte buffer storing an array. <pre><code>char msg_response[]={0x9A,0x17,0x00,0x00,0x17,0x00,0x00,0x00,0x04,0x02,0x9F,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x23,0xEA,0x4A,0x86}; </code></pre> Using memcpy, I expect to map the buffer into the structure. <pre><code> DATABASEPAGEHEADER_TypeDef * varPageHeader; varPageHeader=(DATABASEPAGEHEADER_TypeDef*)malloc(sizeof(DATABASEPAGEHEADER_TypeDef)); memcpy(varPageHeader,msg_response,sizeof(DATABASEPAGEHEADER_TypeDef)); </code></pre> However, the result messes up. Here is the inspection I made using gdb (explore the struct). Things were fine until the ipageNumber, which I expected to have value 0x0000009f.And also later in ireserveX (x=1,2,3). <pre><code>ibaseRecord = 0x179a .. (Value of type 'unsigned int') irecordNumber = 0x17 .. (Value of type 'unsigned int') brecordType = 0x4 .. (Value of type 'unsigned char') brevision = 0x2 .. (Value of type 'unsigned char') ipageNumber = 0x0 .. (Value of type 'unsigned int') ireserve1 = 0x0 .. (Value of type 'unsigned int') ireserve2 = 0x0 .. (Value of type 'unsigned int') ireserve3 = 0xea230000 .. (Value of type 'unsigned int') scrc16 = 0x864a .. (Value of type 'short unsigned int') (gdb) print sizeof(unsigned int) $7 = 0x4 </code></pre> Does anyone have solution to it? problem solved. It was the struct alignment problem. Thank you for your kind help.
Tags
<c><memcpy>
Title
memcpy copying the wrong number of bytes
singulars
PostAcceptedAnswerId
1. PO
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 PTAnswer
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1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USHarryQ
UserOwnerUserId
1. USHarryQ
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PostLinksPostIdRelatedPostId
1. PL
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1. This table or related slice is empty.
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1. This table or related slice is empty.
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1. PO
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2. PO
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1. VO
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 POmemcpy copying the wrong number of bytes
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2. VO
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 POmemcpy copying the wrong number of bytes
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3. VO
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 POmemcpy copying the wrong number of bytes
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