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xstrlcat: Allow overlapped pointers. (#6017)

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memcpy is not equivalent to memmove (which is used by vim_strcat), this
could cause subtle bugs if xstrlcat is used as a replacement for
vim_strcat. But vim_strcat is inconsistent: in the `else` branch it uses
strcpy, which doesn't allow overlap.

Helped-by: oni-link <knil.ino@gmail.com>
Helped-by: James McCoy <jamessan@jamessan.com>
Helped-by: Nikolai Aleksandrovich Pavlov <kp-pav@yandex.ru>
This commit is contained in:
Justin M. Keyes
2017-01-31 17:42:22 +01:00
committed by GitHub
parent d25649fa01
commit 88bc9f8e92
4 changed files with 83 additions and 28 deletions
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51
test/unit/memory_spec.lua Normal file
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@@ -0,0 +1,51 @@
local helpers = require("test.unit.helpers")
local cimport = helpers.cimport
local cstr = helpers.cstr
local eq = helpers.eq
local ffi = helpers.ffi
local to_cstr = helpers.to_cstr
local cimp = cimport('stdlib.h', './src/nvim/memory.h')
describe('xstrlcat()', function()
local function test_xstrlcat(dst, src, dsize)
assert.is_true(dsize >= 1 + string.len(dst)) -- sanity check for tests
local dst_cstr = cstr(dsize, dst)
local src_cstr = to_cstr(src)
eq(string.len(dst .. src), cimp.xstrlcat(dst_cstr, src_cstr, dsize))
return ffi.string(dst_cstr)
end
local function test_xstrlcat_overlap(dst, src_idx, dsize)
assert.is_true(dsize >= 1 + string.len(dst)) -- sanity check for tests
local dst_cstr = cstr(dsize, dst)
local src_cstr = dst_cstr + src_idx -- pointer into `dst` (overlaps)
eq(string.len(dst) + string.len(dst) - src_idx,
cimp.xstrlcat(dst_cstr, src_cstr, dsize))
return ffi.string(dst_cstr)
end
it('concatenates strings', function()
eq('ab', test_xstrlcat('a', 'b', 3))
eq('ab', test_xstrlcat('a', 'b', 4096))
eq('ABCיהZdefgiיהZ', test_xstrlcat('ABCיהZ', 'defgiיהZ', 4096))
eq('b', test_xstrlcat('', 'b', 4096))
eq('a', test_xstrlcat('a', '', 4096))
end)
it('concatenates overlapping strings', function()
eq('abcabc', test_xstrlcat_overlap('abc', 0, 7))
eq('abca', test_xstrlcat_overlap('abc', 0, 5))
eq('abcb', test_xstrlcat_overlap('abc', 1, 5))
eq('abcc', test_xstrlcat_overlap('abc', 2, 10))
eq('abcabc', test_xstrlcat_overlap('abc', 0, 2343))
end)
it('truncates if `dsize` is too small', function()
eq('a', test_xstrlcat('a', 'b', 2))
eq('', test_xstrlcat('', 'b', 1))
eq('ABCיהZd', test_xstrlcat('ABCיהZ', 'defgiיהZ', 10))
end)
end)