{"id":7935,"date":"2022-09-11T01:37:32","date_gmt":"2022-09-10T20:07:32","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-null-as-a-pointer-valid-address-closed\/"},"modified":"2022-09-11T01:37:32","modified_gmt":"2022-09-10T20:07:32","slug":"solved-null-as-a-pointer-valid-address-closed","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-null-as-a-pointer-valid-address-closed\/","title":{"rendered":"[Solved] NULL as a pointer valid address? [closed]"},"content":{"rendered":"

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NULL as a pointer valid address?<\/p>\n<\/blockquote>\n

Maybe: NULL<\/code> is a macro which expands to a null pointer constant<\/em>. It may<\/em> have a value like int<\/code> 0. In that case, it is not a pointer but a int<\/code>. It may<\/em> have a value like ((void*)0)<\/code> which is<\/em> a pointer. When a null pointer constant<\/em> is converted to void *<\/code>, it is a null pointer<\/em>. No object will have an address that is equal to a null pointer<\/em><\/strong>. The null pointer<\/em> can be assigned to any pointer variable.<\/p>\n

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Can we assign or compare a valid pointer with 0? <\/p>\n<\/blockquote>\n

Yes. any_type *ptr = 0;<\/code> is valid. The comparison if (ptr == 0)<\/code> is valid. The int<\/code> 0 is converted to a null pointer<\/em> as part of the assignment \/ compare.<\/p>\n

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where could we assign NULL as legal? <\/p>\n<\/blockquote>\n

any_type *ptr = NULL;<\/code> is a legal assignment. <\/p>\n

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See what I know NULL is a invalid pointer , that pointing to heap memory , which pointer has not freed yet. But is the address of the pointer is valid?<\/p>\n<\/blockquote>\n

The address is or is not valid is irrelevant. Pointing to heap memory or not is irrelevant. In C, assigning a null pointer<\/em> to a pointer variable is<\/strong> valid. Comparing a null pointer<\/em> to a valid object is<\/strong> a valid comparison and the result never matches.<\/p>\n

Dereferencing a pointer that has the value of a null pointer<\/em> is undefined behavior (UB). It may<\/em> “work”, it may<\/em> crash the code. It is UB.<\/p>\n<\/p><\/div>\n

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<\/span> <\/p><\/div>\n<\/div>\n

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solved NULL as a pointer valid address? [closed] <\/p>\n","protected":false},"excerpt":{"rendered":"

[ad_1] NULL as a pointer valid address? Maybe: NULL is a macro which expands to a null pointer constant. It may have a value like int 0. In that case, it is not a pointer but a int. It may have a value like ((void*)0) which is a pointer. When a null pointer constant is … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[324],"class_list":["post-7935","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c"],"yoast_head":"\n[Solved] NULL as a pointer valid address? 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