Re: [Tinycc-devel] BUG: code generation problem in i386-gen.c:gcall_or_jmp()

[张博洋]

OK, I will push my modifications to the mob branch.


在 2017年09月09日 18:26, Christian Jullien 写道:
> Hello Zhang
>
> First I'm not an official maintainer of tcc but a regular user and observer of 
> its evolutions. I also check that it does not regress on the platforms I use.
>
> That said, your recent proposals seem strongly argumented with associated 
> tests. Since no one commented your proposal (that sad!).
> I suggest you to push them in mod so that we can see if we have regression or 
> not with them. Please make one commit at a time for a given fix so that we can 
> better insulate regression (if any).
>
> I any cases, many thanks to participate to this project and to try to make it 
> better.
>
> Christian
>
> -----Original Message-----
> From: Tinycc-devel [mailto:address@hidden On Behalf Of ???
> Sent: samedi 9 septembre 2017 05:03
> To: address@hidden
> Subject: [Tinycc-devel] BUG: code generation problem in 
> i386-gen.c:gcall_or_jmp()
>
> Hello,
>
> I found 3 problems in i386-gen.c:gcall_or_jmp().
>
> (1) There is a fix for extending return value to whole register, however, this 
> fix is in the constant case only, if a call is indirect, this fix will not be 
> applied and the result will be wrong.
>
> (2) The fix is for 'call' and if 'is_jmp' == 1, it will generate redundant code.
>
> (3) Calling constant should use the indirect way. For example, if someone write "((void 
> (*)(void)) 0x12345678)()" in a DLL, the generated code will be "CALL 0x12345678". 
> However, because the imm in CALL instruction is PC related, when the DLL is relocated, the call 
> target will be wrong.
>
>
>
> I provided a patch and two testcase.
>
>
>
> 'test-movzx-movsx.c' is for problem (1) and (2).
> run it with:
>     tcc -run test-movzx-movsx.c
>
> expected output is:
>     0000ABCE 0000ABCE
>     FFFFABCE FFFFABCE
>     000000CE 000000CE
>     FFFFFFCE FFFFFFCE
>
>     0000ABCE 0000ABCE
>     FFFFABCE FFFFABCE
>     000000CE 000000CE
>     FFFFFFCE FFFFFFCE
>
>
>
>
> the other two files are for problem (3).
> run it with:
>
> # set DLL base at 0x400000 to force a relocation tcc -shared 
> -Wl,-Ttext=0x00400000 test-call-constant-dll.c
>
> tcc -L. -ltest-call-constant-dll -run test-call-constant-run.c
>
> expected output is:
>     by pointer variable: FEEDBEEF
>     by pointer constant: FEEDBEEF
>
>
>
>
> Thanks
> Zhang Boyang
>
>
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张博洋 - 复旦大学2014级计算机科学与技术
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