This is necessary for better CGo support on bare metal. Existing
libraries expect to be able to include parts of libc and expect to be
able to link to those symbols.
Because with this all targets have a working libc, it is now possible to
add tests to check that a libc in fact works basically.
Not all parts of picolibc are included, such as the math or stdio parts.
These should be added later, when needed.
This commit also avoids the need for the custom memcpy/memset/memcmp
symbols that are sometimes emitted by LLVM. The C library will take care
of that.
This implementation is still very limited but provides a base to build
upon. Limitations:
* CGO_CFLAGS etc is not taken into account.
* These CFLAGS are not used in C files compiled with the package.
* Other flags (CPPFLAGS, LDFAGS, ...) are not yet implemented.
Instead of putting the magic in the AST, generate regular accessor
methods. This avoids a number of special cases in the compiler, and
avoids missing any of them.
The resulting union accesses are somewhat clunkier to use, but the
compiler implementation has far less coupling between the CGo
implementation and the IR generator.
This commit renames reserved field names like `type` to `_type`, and in
turn renames those fields as well (recursively). This avoids name
clashes when a C struct contains a field named `type`, which is a
reserved keyword in Go.
For some details, see:
https://golang.org/cmd/cgo/#hdr-Go_references_to_C
Previously it was just a combination of heuristics to try to fit a
constant in an *ast.BasicLit. For more complex expressions, this is not
enough.
This change also introduces proper syntax error with locations, if
parsing a constant failed. For example, this will print a real error
message with source location:
#define FOO 5)
Previously, a GenDecl was shared between many different
consts/vars/types. However, it actually makes much more sense not to
bundle them as that is also the case in C.
This makes the printed output of the CGo AST much nicer, and works
around a bug in Go 1.11.
This commit improves diagnostics in a few ways:
* All panics apart from panics with no (easy) recovery are converted to
regular errors with source location.
* Some errors were improved slightly to give more information. For
example, show the libclang type kind as a string instead of a
number.
* Improve source location by respecting line directives in the C
preprocessor.
* Refactor to unify error handling between libclang diagnostics and
failures to parse the libclang AST.
Enum types are implemented as named types (with possible accompanying
typedefs as type aliases). The constants inside the enums are treated as
Go constants like in the Go toolchain.
This is a big commit that does a few things:
* It moves CGo processing into a separate package. It never really
belonged in the loader package, and certainly not now that the
loader package may be refactored into a driver package.
* It adds support for multiple CGo files (files that import package
"C") in a single package. Previously, this led to multiple
definition errors in the Go typecheck phase because certain C
symbols were defined multiple times in all the files. Now it
generates a new fake AST that defines these, to avoid multiple
definition errors.
* It improves debug info in a few edge cases that are probably not
relevant outside of bugs in cgo itself.
