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POPassing pointer to a stack allocated array to function
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16135775
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16135961
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1
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2013-04-21T20:19:42.080
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2013-04-21T20:38:00.790
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2013-04-21T20:35:16.010
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825889
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1
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0
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115
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text
Body
I have a function with the prototype below, the 3rd parameter (output variable) is the only relevant: <pre><code>int ioman_write_pages(void**, unsigned, HDD_address**, /*rest is irrelevant*/) </code></pre> The HDD_address type in case someone asks: <pre><code>typedef union { unsigned long long address; struct { unsigned long long offset : 12; unsigned long long page_number : 26; unsigned long long : 0; } paddress; } HDD_address; </code></pre> Call scenario with heap allocation (Working perfectly): <pre><code>HDD_address* page = (HDD_address*)malloc( pagecount * sizeof(HDD_address) ); memset( page, 0, pagecount * sizeof(HDD_address) ); ioman_write_pages( data, 3, &page, block, NULL, NULL ); printf( "Pages written to: [%d, %d, %d]\n", page[0].address >> 9, page[1].address >> 9, page[2].address >> 9 ); </code></pre> Output (Expected: 0, 16, 24): <pre><code>Pages written to: [0, 16, 24] </code></pre> The above heap allocation works no problem. If however I attempt a stack allocation of "page": <pre><code>HDD_address page[pagecount]; memset( page, 0, pagecount * sizeof(HDD_address) ); ioman_write_pages( data, 3, &page, block, NULL, NULL ); </code></pre> Output, while data wise nonsensical, it is consistent: <pre><code>Pages written to: [166956, 0, 0] </code></pre> Compile warning when compiling the above: <pre><code>note: expected ‘union HDD_address **’ but argument is of type ‘union HDD_address (*)[(sizetype)(pagecount)]’ </code></pre> Stack allocation, "fixing" the warning: <pre><code>DD_address page[pagecount]; memset( page, 0, pagecount * sizeof(HDD_address) ); HDD_address* ppage = page; int r = ioman_write_pages( data, 3, &ppage, block, NULL, NULL ); </code></pre> Output, again consistent every run but nonsense: <pre><code>Pages written to: [1610376, 2856870, 610607] </code></pre> I cannot make any sense of this at all, someone please enlighten me!
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<c><function><stack><parameter-passing><allocation>
Title
Passing pointer to a stack allocated array to function
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1. PO
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1. This table or related slice is empty.
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1. PTQuestion
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1. USSkod
UserOwnerUserId
1. USSkod
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1. PO
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