错误C2227：“-> yr”的左侧必须指向类/结构/联合/泛型类型

Question

I'm writing encrypt/decrypt program for WinCE.

When I compile the program i get errors like: error C2227: left of '->yr' must point to class/struct/union/generic type

The snippet for this is:

void ai(struct AES_ctx* ctx, const uint8_t* key)
{
  k(ctx->yr, key);
}

and the corresponding header snippet:

#define AES_BLOCKLEN 16
#define AES_KEYLEN 32
#define AES_keyExpSize 240

struct AES_ctx
{
  uint8_t yr[AES_keyExpSize];
  uint8_t Iv[AES_BLOCKLEN];
};

void ai(struct AES_ctx* ctx, const uint8_t* key);

With StandardSDK_500 ARMv4I compiler works fine, but with MIPSII I got this.

Can anybody help to resolve this error?

Answer 1

There is nothing wrong with your code: it compiles fine.

(if ctx is a macro, defined in some #included header file, all sorts of errors could be produced by this code, including the one you report, and this could be compiler dependent; test with #ifdef ctx ... )

You may want to run the pre-processor (typically with the option -E ) and look at the code produced.

(As a side remark, in C++ this looks more like

namespace AES {
    constexpr int blocklen=16;
    constexpr int keylen=32;
    constexpr int keyExpSize=240;

    struct ctx {
        std::uint8_t yr[keyExpSize];
        std::uint8_t Iv[blocklen];
    };
    // etc
}

ie no macros, no pollution of global namespace.)