function parameters of go always pass value

This is a creation in Article, where the information may have evolved or changed.

According to the fqa of Go, the parameters of the function are always passed the value (pass-by-value):

As in all languages with the C family, everything in Go are passed by value. That's, a function always gets a copy of the thing being passed, as if there were an assignment statement assigning the V Alue to the parameter. For instance, passing an int value to a function makes a copy of the int, and passing a pointer value makes a copy of the Pointer, but isn't the data it points to. (see a later sections for a discussion of what this affects method receivers.)

Map and slice values behave like pointers:they is descriptors that contain pointers to the underlying map or slice data. Copying a map or slice value doesn ' t copy the data it points to. Copying an interface value makes a copy of the thing stored in the interface value. If the interface value holds a struct, copying the interface value makes a copy of the struct. If the interface value holds a pointer, copying the interface value makes a copy of the pointer, but again not the data it Points to.

The following is the test code, the results are posted below, not explained.

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PackageMainImport("FMT""Reflect""unsafe")funcPrintint (iint) {FMT. Printf ("int i:%p\n", &i)}funcPrintInt2 (i *int) {FMT. Printf ("int i:%p\n", i)}funcPRINTSTR (Sstring) {FMT. Printf ("string s:%p\n", &s) HDR: = (*reflect. Stringheader) (unsafe. Pointer (&s)) Data: = HDR. datafmt.printf ("string s data:0x%x\n", data)}funcPRINTSTR2 (S *string) {FMT. Printf ("string s:%p\n", s) HDR: = (*reflect. Stringheader) (unsafe. Pointer (s)) Data: = HDR. datafmt.printf ("string s data:0x%x\n", data)}funcPrintslice (S []int) {FMT. Printf ("Slice s:%p\n", &s) HDR: = (*reflect. Sliceheader) (unsafe. Pointer (&s)) Data: = HDR. datafmt.printf ("Slice s data:0x%x\n", data)}funcPrintSlice2 (S *[]int) {FMT. Printf ("Slice s:%p\n", s) HDR: = (*reflect. Sliceheader) (unsafe. Pointer (s)) Data: = HDR. datafmt.printf ("Slice s data:0x%x\n", data)}typeSstruct{Iint}funcPrintstruct (s s) {FMT. Printf ("struct S:%p, I:%p\n", &s, & (S.I))}funcPrintStruct2 (s *s) {fmt. Printf ("struct S:%p, I:%p\n", &s, & (S.I))}funcPrintinterface (iInterface{}) {Fmt. Printf ("int i:%p\n", &i)}funcPrintInterface2 (iInterface{}) {s: = i. (s) fmt. Printf ("struct S:%p, I:%p\n", &s, & (S.I))}funcPrintInterface3 (iInterface{}) {s: = I. (*S) FMT. Printf ("struct S:%p, I:%p\n", S, & (S.I))}funcMain () {//test intI: =TenFmt. Printf ("int i:%p\n", &i) Printint (i) PrintInt2 (&i)//test StringS: ="Hello, World"Fmt. Printf ("\n\nstring s:%p\n", &s) HDR: = (*reflect. Stringheader) (unsafe. Pointer (&s)) Data: = HDR. datafmt.printf ("string s data:0x%x\n", data) Printstr (s) printStr2 (&s)//slice and MapSL: = []int{1,2,3,4,5}fmt. Printf ("\n\nslice s:%p\n", &SL) HDR2: = (*reflect. Sliceheader) (unsafe. Pointer (&SL)) data = HDR2. datafmt.printf ("Slice s data:0x%x\n", data) Printslice (SL) PrintSlice2 (&SL)//structSS: = s{i:Ten}SSP: = &ssfmt. Printf ("\n\nstruct s:%p, I:%p\n", SSP, & (ss. I)) printstruct (ss) PrintStruct2 (SSP)//interface to intFmt. Printf ("\n\nint I:%p\n", &i) printinterface (i)//interface to structFmt. Printf ("\n\nstruct s:%p, I:%p\n", SSP, & (ss. I)) PrintInterface2 (ss) PrintInterface3 (SSP)}

Output Result:

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intI0xc420074188intI0xc4200741b8intI0xc420074188string s:0xc4200741c0string s data:0xa778dstring s:0xc4200741e0string s data:0xa778dstring s:0xc4200741c0string s data:0xa778dSlice s:0xc42006e0c0Slice s data:0xc4200780c0Slice s:0xc42006e0e0Slice s data:0xc4200780c0Slice s:0xc42006e0c0Slice s data:0xc4200780c0struct S:0xc420074210, I:0xc420074210struct S:0xc420074218, I:0xc420074218struct S:0xc420084020, I:0xc420074210intI0xc420074188intI0xc420074230struct S:0xc420074210, I:0xc420074210struct S:0xc420074228, I:0xc420074228struct S:0xc420074210, I:0xc420074210