Possible ODR violation

[SchrodingerZhu]

I encountered the following with gcc 10.2.0:

../src/test/func/two_alloc_types/main.cc:37:1: warning: ‘host_snmalloc_chunkmap_global_get’ violates the C++ One Definition Rule [-Wodr]
   37 | host_snmalloc_chunkmap_global_get(snmalloc::PagemapConfig const**);
      | ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type mismatch in parameter 1
  224 |   SNMALLOC_EXPORT void* SNMALLOC_NAME_MANGLE(snmalloc_chunkmap_global_get)(
      |                         ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type name ‘snmalloc_host::PagemapConfig’ should match type name ‘snmalloc::PagemapConfig’
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: ‘host_snmalloc_chunkmap_global_get’ was previously declared here
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
../src/test/func/two_alloc_types/main.cc:35:1: warning: ‘enclave_snmalloc_chunkmap_global_get’ violates the C++ One Definition Rule [-Wodr]
   35 | enclave_snmalloc_chunkmap_global_get(snmalloc::PagemapConfig const**);
      | ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type mismatch in parameter 1
  224 |   SNMALLOC_EXPORT void* SNMALLOC_NAME_MANGLE(snmalloc_chunkmap_global_get)(
      |                         ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type name ‘snmalloc_enclave::PagemapConfig’ should match type name ‘snmalloc::PagemapConfig’
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: ‘enclave_snmalloc_chunkmap_global_get’ was previously declared here
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
[107/211] Linking CXX executable func-two_alloc_types-1
../src/test/func/two_alloc_types/main.cc:37:1: warning: ‘host_snmalloc_chunkmap_global_get’ violates the C++ One Definition Rule [-Wodr]
   37 | host_snmalloc_chunkmap_global_get(snmalloc::PagemapConfig const**);
      | ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type mismatch in parameter 1
  224 |   SNMALLOC_EXPORT void* SNMALLOC_NAME_MANGLE(snmalloc_chunkmap_global_get)(
      |                         ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type name ‘snmalloc_host::PagemapConfig’ should match type name ‘snmalloc::PagemapConfig’
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: ‘host_snmalloc_chunkmap_global_get’ was previously declared here
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
../src/test/func/two_alloc_types/main.cc:35:1: warning: ‘enclave_snmalloc_chunkmap_global_get’ violates the C++ One Definition Rule [-Wodr]
   35 | enclave_snmalloc_chunkmap_global_get(snmalloc::PagemapConfig const**);
      | ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type mismatch in parameter 1
  224 |   SNMALLOC_EXPORT void* SNMALLOC_NAME_MANGLE(snmalloc_chunkmap_global_get)(
      |                         ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type name ‘snmalloc_enclave::PagemapConfig’ should match type name ‘snmalloc::PagemapConfig’
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: ‘enclave_snmalloc_chunkmap_global_get’ was previously declared here
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
[195/211] Linking CXX executable func-two_alloc_types-oe
../src/test/func/two_alloc_types/main.cc:37:1: warning: ‘host_snmalloc_chunkmap_global_get’ violates the C++ One Definition Rule [-Wodr]
   37 | host_snmalloc_chunkmap_global_get(snmalloc::PagemapConfig const**);
      | ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type mismatch in parameter 1
  224 |   SNMALLOC_EXPORT void* SNMALLOC_NAME_MANGLE(snmalloc_chunkmap_global_get)(
      |                         ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type name ‘snmalloc_host::PagemapConfig’ should match type name ‘snmalloc::PagemapConfig’
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: ‘host_snmalloc_chunkmap_global_get’ was previously declared here
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used
../src/test/func/two_alloc_types/main.cc:35:1: warning: ‘enclave_snmalloc_chunkmap_global_get’ violates the C++ One Definition Rule [-Wodr]
   35 | enclave_snmalloc_chunkmap_global_get(snmalloc::PagemapConfig const**);
      | ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type mismatch in parameter 1
  224 |   SNMALLOC_EXPORT void* SNMALLOC_NAME_MANGLE(snmalloc_chunkmap_global_get)(
      |                         ^
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: type name ‘snmalloc_enclave::PagemapConfig’ should match type name ‘snmalloc::PagemapConfig’
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: ‘enclave_snmalloc_chunkmap_global_get’ was previously declared here
../src/test/func/two_alloc_types/../../../override/malloc.cc:224:25: note: code may be misoptimized unless ‘-fno-strict-aliasing’ is used

[mjp41]

Looks like

extern "C" void*
enclave_snmalloc_chunkmap_global_get(snmalloc::PagemapConfig const**);
extern "C" void*
host_snmalloc_chunkmap_global_get(snmalloc::PagemapConfig const**);

in main.cc should be

extern "C" void*
enclave_snmalloc_chunkmap_global_get(snmalloc_enclave::PagemapConfig const**);
extern "C" void*
host_snmalloc_chunkmap_global_get(snmalloc_host::PagemapConfig const**);

But then the comparison of pagemap config will complain. @davidchisnall might have some thoughts on the right way to fix this. We might need to create an snmalloc_abi namespace to deal with this correctly, so that the config is just defined once.