bind: pass &v[0] in direct call to C #267
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In Go 1.6, the cgo checking rules are more precise when they see an address operation as an argument to the C function. When you pass &v[0] to a C function, the cgo check just verifies that v itself does not contain any pointers. When you write `p := &v[0]` and then pass p to the C function, the cgo check is conservative: it verifies that the entire memory block to which p points does not contain any pointers. When the bind function is called by code that passes a slice that is part of a larger struct, this means that the cgo check will look at the entire larger struct, not just the slice. This can cause a surprising run time failure. Avoid this problem by rewriting the code slightly to pass &v[0] in the call to the C function itself. In particular this fixes the tests of github.com/jmoiron/sqlx when using Go 1.6.
mattn
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Feb 1, 2016
bind: pass &v[0] in direct call to C
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I see. Thank you. |
vanadium-bot
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Mar 14, 2016
Motivation: To make things work with Go 1.6 Specifically to get this mattn/go-sqlite3#267 and mattn/go-sqlite3#268 Change-Id: I66daa419daebfddf1382ade56af4d1806eebf409
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In Go 1.6, the cgo checking rules are more precise when they see an
address operation as an argument to the C function. When you pass &v[0]
to a C function, the cgo check just verifies that v itself does not
contain any pointers. When you write
p := &v[0]and then pass p tothe C function, the cgo check is conservative: it verifies that the
entire memory block to which p points does not contain any pointers.
When the bind function is called by code that passes a slice that is
part of a larger struct, this means that the cgo check will look at the
entire larger struct, not just the slice. This can cause a surprising
run time failure.
Avoid this problem by rewriting the code slightly to pass &v[0] in the
call to the C function itself.
In particular this fixes the tests of github.com/jmoiron/sqlx when using
Go 1.6.