35 lines
1.4 KiB
Plaintext
35 lines
1.4 KiB
Plaintext
;;;; A string literal handed to a declare-c goes to C uncopied; any other string
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;;;; is copied and terminated.
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;;;;
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;;;; basename is bound for the pointer it returns, which for a name with no
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;;;; slash in it is the pointer it was given: the literal's own address in the
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;;;; program image for the first call, and the wrapper's stack buffer for the
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;;;; second, whose string is a local and gets the copy. The two are far apart
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;;;; only when the literal was not copied.
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;;;;
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;;;; puts then shows the bytes C read: the literal, the empty literal, and a
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;;;; sub-view that has no NUL after it and so must still be copied.
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;;;;
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;;;; c-where2 is the same question through a signature with a struct in it,
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;;;; which the shim answers with a Flan wrapper over a flattened declaration:
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;;;; the literal has to pass through that wrapper. It binds glibc's POSIX
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;;;; basename, which answers the same pointer and ignores the extra argument.
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(defstruct Ch [c i32])
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(declare-c c-where [s str] i64 "basename")
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(declare-c c-where2 [s str c Ch] i64 "__xpg_basename")
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(declare-c c-puts [s str] i32 "puts")
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(defn is-far [a i64 b i64] bool
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(let [d (- a b)]
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(> (if (< d 0) (- 0 d) d) 1048576)))
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(defn main [] i32
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(let [s "hello"]
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(println (is-far (c-where "hello") (c-where s)))
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(println (is-far (c-where2 "hello" (Ch {.c 104})) (c-where2 s (Ch {.c 104}))))
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(c-puts "hello")
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(c-puts "")
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(c-puts (str (slice (bytes-view "hello world") 0 3))))
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0)
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