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This article mainly introduces the C++ pointer parameter transmission essence and how to use the secondary pointer related knowledge, the content is detailed and easy to understand, the operation is simple and fast, has a certain reference value, I believe that after reading this C++ pointer parameter transmission essence and how to use the secondary pointer article will have a harvest, let's take a look.

Let's first look at two programs:

1:

Void test (char * p)

{

Printf ("[test1] [p]:% p.\ n", p)

Printf ("[test2] [p]:% s.\ n", p)

P = (char *) malloc (10)

Strcpy (p, "ABCDE")

Printf ("[test3] malloc after.\ n")

Printf ("[test4] [p]:% p.\ n", p)

Printf ("[test5] [p]:% s.\ n", p)

Free (p)

}

Int main ()

{

Char b [6] = "abcde"

Char * a = b

Printf ("[main1] [a]:% p.\ n", a)

Printf ("[main2] [a]:% s.\ n", a)

Test (a)

Printf ("[main3] [a]:% p.\ n", a)

Printf ("[main4] [a]:% s.\ n", a)

Return 0

}

Output: note: (the pde value of the test function has changed, but the value of an of the main function has not changed)

Main1] [a]: 0xbfeaaef6.

[main2] [a]: abcde.

[test1] [p]: 0xbfeaaef6.

[test2] [p]: abcde.

[test3] after malloc.

[test4] [p]: 0x8a52008.

[test5] [p]: ABCDE.

[main3] [a]: 0xbfeaaef6.

[main4] [a]: abcde.

2:

Void test (char * * p)

{

Printf ("[test1] [p]:% p.\ n", p)

Printf ("[test2] [* p]:% p.\ n", * p)

* p = (char *) malloc (10)

Strcpy (* p, "ABCDE")

Printf ("[test3] malloc after.\ n")

Printf ("[test4] [p]:% p.\ n", p)

Printf ("[test5] [* p]:% p.\ n", * p)

Printf ("[test6] [* p]:% s.\ n", * p)

Free (* p)

}

Int main ()

{

Char b [6] = "abcde"

Char * a = b

Printf ("[main1] [a]:% p.\ n", a)

Printf ("[main2] [a]:% s.\ n", a)

Test & a)

Printf ("[main3] [a]:% p.\ n", a)

Printf ("[main4] [a]:% s.\ n", a)

Return 0

}

Output: note: (the pde value of the test function has changed, and the value of an of the main function has also changed)

[main1] [a]: 0xbfaca776.

[main2] [a]: abcde.

[test1] [p]: 0xbfaca770.

[test2] [* p]: 0xbfaca776.

[test3] after malloc.

[test4] [p]: 0xbfaca770.

[test5] [* p]: 0x9132008.

[test6] [* p]: ABCDE.

[main3] [a]: 0x9132008.

[main4] [a]: ABCDE.

This is the end of the article on "the essence of C++ pointer parameter transmission and how to use the secondary pointer". Thank you for reading! I believe that everyone has a certain understanding of the "C++ pointer parameter transmission essence and how to use the secondary pointer" knowledge, if you want to learn more knowledge, welcome to follow the industry information channel.

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