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

[张博洋]

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

fixcall.patch
Description: Text Data

test-call-constant-dll.c
Description: Text Data

test-call-constant-run.c
Description: Text Data

test-movzx-movsx.c
Description: Text Data