I have read about problems with loading structs from file. There are problems with endianness and different variable sizes. But let us say that there is a structure like this one:
struct Structure
{
uint8_t value1;
uint16_t value2;
uint32_t value3;
uint64_t value;4
};
Let us say that the file is always written in little-endian format, so application reads it in strict way. In such case endianness should not cause any problems. (Let us assume that there is some kind of convertEndinness() function which is clever enough to omit byte order issue). The second thing which I know is neccesery to consider is variable size variety. There is my question. Do fixed size types manage to handle this problem and what else should I consider in order to create multiplatform binary file?
Do fixed size types manage to handle this problem
Not quite.
The fixed-size types have fixed sizes, but their alignment requirements (and therefore padding) may vary between platforms and/or ABI flavours. So, your struct could still have different layout on different platforms even with the same endianness.
You can insist that there should be no padding, and use some compiler-specific and non-standard way to specify this (like #pragma pack or __attribute__((packed))). This can produce worse code for accessing misaligned members directly, though.
what else should I consider in order to create multiplatform binary file?
If you choose an endianness, use fixed-size types and specify the alignment correctly, you're probably fine.
I'd strongly suggested adding a header and/or some framing information, with a version and possibly some metadata about the sizes and alignments you chose. Otherwise you can never change this file format in the future without things breaking in unpleasant ways.