Call a foreign-language function: Difference between revisions

=={{header|FreeBASIC}}==

Normally it's an easy matter to call a function in the C Standard Library, statically, from FreeBASIC.

However, 'strdup' isn't in the Standard Library so instead we will call the version in the Windows Shell, dynamically.

As this uses LocalAlloc in kernel32.dll internally to allocate memory for the duplicated string, we need to call

LocalFree to free this memory using the pointer returned by strdup.

<lang freebasic>' FB 1.05.0 Win64

'Using StrDup function in Shlwapi.dll

Dim As Any Ptr library = DyLibLoad("Shlwapi")

Dim strdup As Function (ByVal As Const ZString Ptr) As ZString Ptr

strdup = DyLibSymbol(library, "StrDupA")

'Using LocalFree function in kernel32.dll

Dim As Any Ptr library2 = DyLibLoad("kernel32")

Dim localfree As Function (ByVal As Any Ptr) As Any Ptr

localfree = DyLibSymbol(library2, "LocalFree")

Dim As ZString * 10 z = "duplicate" '' 10 characters including final zero byte

Dim As Zstring Ptr pcz = strdup(@z) '' pointer to the duplicate string

Print *pcz '' print duplicate string by dereferencing pointer

localfree(pcz) '' free the memory which StrDup allocated internally

pcz = 0 '' set pointer to null

DyLibFree(library) '' unload first dll

DyLibFree(library2) '' unload second fll

End</lang>

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<pre>

duplicate

</pre>