Fix crash by implementing a custom malloc

Ref https://surma.dev/things/c-to-webassembly/

README.md

@@ -1,3 +1,8 @@
 # osfs-wasm
 
-Compiling the Over-Simplified FileSystem to WASM for fun and profit
+> Compiling the Over-Simplified FileSystem to WASM for fun and profit
+
+
+
+
+EEPROM sizes, ref <https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-8867-SEEPROM-Products-Brochure.pdf> (which suggests kilo**bit**s?!) and <http://ww1.microchip.com/downloads/en/DeviceDoc/21189f.pdf> (which suggests KiB)

src/wasm/compile-wasm.sh

@@ -31,15 +31,15 @@ task_begin "Compile";
 
 echo -e ">>> Working directory is ${HC}${PWD}${RS}" >&2;
 
-execute clang -v -v -v --target=wasm32 -nostdlib -Wl,--export-all -Wl,--no-entry \
+execute clang --target=wasm32 -nostdlib -Wl,--export-all -Wl,--no-entry \
 	-I"${dirpath_include}" \
 	-I "${dirpath_walloc}" \
 	-I "${dirpath_osfs}" \
 	-o "${dirpath_output}/osfs.wasm" \
-	"${dirpath_walloc}/walloc.c" \
 	"${dirpath_osfs}/OSFS.cpp" \
 	"${dirpath_include}/wrapper.cpp" \
 	;
 
+	# "${dirpath_walloc}/walloc.c" \
 
 task_end "${?}";

src/wasm/include/wrapper.cpp

@@ -1,6 +1,27 @@
 #include "Arduino.h"
 #include "OSFS.h"
-#include <walloc.h>
+
+// -------------------------------------------------------------------------
+
+// Custom malloc implementation
+// Initial design ref https://surma.dev/things/c-to-webassembly/ → Building an
+// allocator
+
+// This started as a simple bump allocator, but we've turned it into a singleton
+// allocator that always allocates the same area of memory, since we only want to allocate a single area of memory
+extern unsigned char __heap_base;
+
+unsigned int bump_pointer = (unsigned int)&__heap_base;
+void *malloc(int n) {
+	unsigned int r = bump_pointer; // This works because the heap grows *upwards* in WASM, not downwards
+	//   bump_pointer += n; 
+	
+	return (void *)r;
+}
+
+void free(void *p) {
+	// lol
+}
 
 // -------------------------------------------------------------------------
 
@@ -51,29 +72,27 @@ OSFS::result result;
 uint16_t OSFS::startOfEEPROM = 1;
 uint16_t OSFS::endOfEEPROM = 64; // change w/set_eeprom_size
 
+byte *memory = (byte*)malloc((size_t)(64 * 1024)); // virtual EEPROM, default 64KiB
 
-byte* memory = (byte*)malloc((size_t)(64*1024)); // virtual EEPROM, default 64KiB
-
-void __create_memory(uint32_t size) {
-	free((void*)memory);
-	void* memory_raw = malloc((size_t)(size * 1024));
-	memory = (byte*)memory_raw;
+void __clear_memory(uint32_t size) {
+	memset(memory, 0, (size_t)(size * 1024));
 }
 
-
-
+void __create_memory(uint32_t size) {
+	free((void *)memory);
+	void *memory_raw = malloc((size_t)(size * 1024));
+	memory = (byte *)memory_raw;
+}
 
 // -------------------------------------------------------------------------
 
 // Error handling
 
-#define ERROR_OUT_OF_BOUNDS	1
+#define ERROR_OUT_OF_BOUNDS 1
 
 int last_error = 0;
 
-int get_last_error() {
-	return last_error;
-}
+int get_last_error() { return last_error; }
 
 // -------------------------------------------------------------------------
 
@@ -90,20 +109,14 @@ void set_eeprom_size(uint16_t new_size) {
 	__create_memory(new_size);
 }
 
-uint16_t get_eeprom_size() {
-	return OSFS::endOfEEPROM;
-}
-uint32_t get_eeprom_size_bytes() {
-	return OSFS::endOfEEPROM * 1024;
-}
+uint16_t get_eeprom_size() { return OSFS::endOfEEPROM; }
+uint32_t get_eeprom_size_bytes() { return OSFS::endOfEEPROM * 1024; }
 
-
-
-void OSFS::readNBytes(uint16_t address, unsigned int num, byte* output) {
+void OSFS::readNBytes(uint16_t address, unsigned int num, byte *output) {
 	// eeprom.read(address, output, num);
 	last_error = 0;
 
-	if(address < OSFS::startOfEEPROM || address + num > OSFS::endOfEEPROM * 1024) {
+	if (address < OSFS::startOfEEPROM || address + num > OSFS::endOfEEPROM * 1024) {
 		last_error = ERROR_OUT_OF_BOUNDS;
 		return;
 	}
@@ -111,9 +124,8 @@ void OSFS::readNBytes(uint16_t address, unsigned int num, byte* output) {
 	for (unsigned int i = 0; i < num; i++) {
 		output[i] = memory[address + i];
 	}
-	
 }
-void OSFS::writeNBytes(uint16_t address, unsigned int num, const byte* input) {
+void OSFS::writeNBytes(uint16_t address, unsigned int num, const byte *input) {
 	// eeprom.write(address, input, num);
 	last_error = 0;