On Windows, the symbols "___stop___sancov_guards" and "___start___sancov_guards"
are not defined automatically. So, we need to take a different approach.
We define 3 sections: ".SCOV$A", ".SCOV$M" and ".SCOV$Z".
Section ".SCOV$A" will only hold a variable ___start___sancov_guard.
Section ".SCOV$M" will hold the main data.
Section ".SCOV$Z" will only hold a variable ___stop___sancov_guards.
When linking, they will be merged sorted by the characters after the $, so we
can use the pointers of the variables ___[start|stop]___sancov_guard to know the
actual range of addresses of that section.
___[start|stop]___sancov_guard should be defined only once per module. On
Windows, we have 2 different cases:
+ When considering a shared runtime:
All the modules, main executable and dlls, are linked to an auxiliary static
library dynamic_runtime_thunk.lib. Because of that, we include the delimiters
in `SancovDynamicRuntimeThunk`.
+ When considering a static runtime:
The main executable in linked to the static runtime library.
All the dlls are linked to an auxiliary static library dll_thunk.
Because of that, we include the delimiter to both `SancovDllThunk` and
`SANITIZER_LIBCDEP_SOURCES` (which is included in the static runtime lib).
Differential Revision: https://reviews.llvm.org/D28435
llvm-svn: 293959
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