fix #361, no good error on overflow of mutation buffer

VERSIONS

@@ -116,6 +116,7 @@ development head (in the master branch):
 	fix a bug with the Species methods mutationCounts() / mutationFrequences(), only for multispecies models; counts/frequencies would be zero for some species
 		this did not occur when running under SLiMgui (different code path), but always happened at the command line
 	add rank() function to Eidos (https://github.com/MesserLab/SLiM/issues/379); identical to R except that logical and string are not supported, and "random" is not supported; can be added later as needed
+	bug fix: #361, more than 2 billion mutations overflows without a good error message
 	bug fix in pyslim to announce: https://github.com/tskit-dev/pyslim/issues/307
 
 

core/mutation.cpp

@@ -106,13 +106,25 @@ void SLiM_IncreaseMutationBlockCapacity(void)
 	std::uintptr_t old_mutation_block = reinterpret_cast<std::uintptr_t>(gSLiM_Mutation_Block);
 	MutationIndex old_block_capacity = gSLiM_Mutation_Block_Capacity;
 
+	//std::cout << "old capacity: " << old_block_capacity << std::endl;
+
+	// BCH 25 July 2023: check for increasing our block beyond the maximum size of 2^31 mutations.
+	// See https://github.com/MesserLab/SLiM/issues/361.  Note that the initial size should be
+	// a power of 2, so that we actually reach the maximum; see SLIM_MUTATION_BLOCK_INITIAL_SIZE.
+	// In other words, we expect to be at exactly 0x0000000040000000UL here, and thus to double
+	// to 0x0000000080000000UL, which is a capacity of 2^31, which is the limit of int32_t.
+	if ((size_t)old_block_capacity > 0x0000000040000000UL)	// >2^30 means >2^31 when doubled
+		EIDOS_TERMINATION << "ERROR (SLiM_IncreaseMutationBlockCapacity): too many mutations; there is a limit of 2^31 (2147483648) segregating mutations in SLiM." << EidosTerminate(nullptr);
+
 	gSLiM_Mutation_Block_Capacity *= 2;
 	gSLiM_Mutation_Block = (Mutation *)realloc((void*)gSLiM_Mutation_Block, gSLiM_Mutation_Block_Capacity * sizeof(Mutation));
 	gSLiM_Mutation_Refcounts = (slim_refcount_t *)realloc(gSLiM_Mutation_Refcounts, gSLiM_Mutation_Block_Capacity * sizeof(slim_refcount_t));
 
 	if (!gSLiM_Mutation_Block || !gSLiM_Mutation_Refcounts)
 		EIDOS_TERMINATION << "ERROR (SLiM_IncreaseMutationBlockCapacity): allocation failed; you may need to raise the memory limit for SLiM." << EidosTerminate(nullptr);
 
+	//std::cout << "new capacity: " << gSLiM_Mutation_Block_Capacity << std::endl;
+
 	std::uintptr_t new_mutation_block = reinterpret_cast<std::uintptr_t>(gSLiM_Mutation_Block);
 
 	// Set up the free list to extend into the new portion of the buffer.  If we are called when