[Main] Title=Conditional Reaction to Global Imports Index=..._AND_..., NOT_... [Top] Sometimes, it is convenient for an archive member to react to a global import differently than just to be included whenever the import is created. For example, a startup section may be optimized better if a certain register already holds a certain value, otherwise it must compute the value by itself. The TIGCC linker defines two symbol operators for this purpose:
A_AND_B
. To be
included only if the global import A is not defined, a file must
export the symbol NOT_A
. Symbol operators may be
combined, i.e. a file exporting NOT_A_AND_B
is
included only if no global import A exists, and a global import
B is defined.
NOT_A
or
NOT_B
needs to be imported. However, the file which
exported NOT_B
may actually create a global import
A after the file exporting NOT_A
has been
imported. The linker does not detect this, so you need to be careful not to
create such situations. They are especially difficult to detect if a lot of
combinations of AND and NOT operators are used, and if a lot of files that
react to global imports create imports of their own.