64位项目中的32位.obj

Question

I have a 32-bit object file o.obj and want to use it in a project that uses a 64-bit library l.lib .

To make the .lib happy, the Visual Studio configuration needs to be set to x64. However, the linker then throws an error of error LNK1112: module machine type 'X86' conflicts with target machine type 'x64' .

I went through Visual Studio's linker options, but nothing jumped out. Is there a way to resolve this error?

I was under the impression that any 32-bit code is also compatible with 64-bit systems, modulo libraries.

Answer 1

x86 executables (that is, object code compiled for 32-bit x86 processors) can be executed on x64 machines running 64-bit operating systems, through a special compatibility mode supported jointly by the processor and the operating system. This is feasible because the x86 instruction set is a subset of the x64 instruction set.

However, many elements of the ABI differ between x86 and x64 code, notably calling conventions and pointer size. The calling convention needs to match between the calling code and the called code, or things will screw up. Thus, there is no straightforward way to call 64-bit code from 32-bit code, or vice versa.