Re: `string.unpack` 's bug in option `z`

[Dirk Laurie <dirk.laurie@...>]

Op Ma., 3 Sep. 2018 om 12:08 het actboy168 <actboy168@gmail.com> geskryf:
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> But the struct library will raise an error.

True, but that error is:
   bad argument #1 to 'unpack' (invalid format option 'z')
I.e. the option 'z' is an addition available in the Lua 5.3 library version.

> 发件人: Dirk Laurie
> 发送时间: 2018年9月3日 17:52
> 收件人: Lua mailing list
> 主题: Re: `string.unpack` 's bug in option `z`
>
>
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> Op Ma., 3 Sep. 2018 om 04:29 het actboy168 <actboy168@gmail.com> geskryf:
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>
>
> > Lua 5.3.5  Copyright (C) 1994-2018 Lua.org, PUC-Rio
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> >
>
> > > print(string.unpack('z', 'ABC'))
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> > ABC     5
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> > This is not a zero-terminated string, so I think lua should raise an error.
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>
>
> You are right that 'ABC' is not a zero-terminated string, but I do not
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> agree that Lua should raise an error. The manual says 'All integral
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> options check overflows; ... string.unpack checks whether the read
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> value fits in a Lua integer.' There is no risk of overflow here, so an
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> error should not be raised, and the manual almost says so: 'Options
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> "c" and "z" are not aligned'.
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>
>
> The string pack/unpack routines are taken from Roberto's 'struct'
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> library http://www.inf.puc-rio.br/~roberto/struct/, which has been in
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> existence for at least six years (timestamp on the makefile).
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>
>
> BTW that library is a beautiful example of how to write C API code
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> that compiles on all Lua versions from 5.0 to 5.4 with only this
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> version-dependent test:
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>
>
> #if (LUA_VERSION_NUM >= 502)
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> #define luaL_register(L,n,f)    luaL_newlib(L,f)
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> #endif
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>
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>