Structure layout
Structure layout must match the target ABI when FreeBASIC code talks to C
libraries, system calls, graphics backends, sound backends, or binary file
formats. Do not assume that a structure layout proven on one CPU is correct on
another CPU.
What affects layout
Layout-sensitive code should be checked on every advertised CPU family. That
includes 32-bit and 64-bit x86, ARM, AArch64, PowerPC-family targets,
MIPS-family targets, s390x, WebAssembly/JavaScript where applicable, and the
BSD, Haiku, Solaris-like, DOS, Windows, and mobile targets supported by the
tree.
Practical rule
When a structure is shared with C, prefer a tiny C probe or a FreeBASIC test that
checks sizeof and important field offsets on the real target. Guessing from
a similar platform is not enough for release work.
Structure layout must match the target ABI when FreeBASIC code talks to C
libraries, system calls, graphics backends, sound backends, or binary file
formats. Do not assume that a structure layout proven on one CPU is correct on
another CPU.
What affects layout
Field type and size.
Field alignment.
Structure packing.
Pointer size.
Calling convention and ABI family.
Compiler-specific C headers for the target platform.
Modern targetsField alignment.
Structure packing.
Pointer size.
Calling convention and ABI family.
Compiler-specific C headers for the target platform.
Layout-sensitive code should be checked on every advertised CPU family. That
includes 32-bit and 64-bit x86, ARM, AArch64, PowerPC-family targets,
MIPS-family targets, s390x, WebAssembly/JavaScript where applicable, and the
BSD, Haiku, Solaris-like, DOS, Windows, and mobile targets supported by the
tree.
Practical rule
When a structure is shared with C, prefer a tiny C probe or a FreeBASIC test that
checks sizeof and important field offsets on the real target. Guessing from
a similar platform is not enough for release work.