DevOps, CI/CD and Automation

I want to read 3rd party genaterated binary data e.g.

struct t_simple_str
{
     char c;
     double d;
};

where d has an offset of 8 byte.

Using SunStudio's 12U1 cc 32-bit compiler on Linux the default offset of d is 4 but with

struct t_simple_str
{
	char c;
	double d __attribute__((aligned(8)));
};

I can achieve that th double is recognized at the correct offset.

Since I have to use the C++ compiler that doesn't support __attribute__((aligned(8)))
I want to know if there is a equivalent feature that calculates the correct offset.

I did some unsuccessful tests with #pragma align 8 (...)
but according documentation it doesn't work on local variables.

Can anybody give me a hint?