Weird pointer conversion in C - c

Question

I'm having trouble while writing my garbage collector in C. I give you a minimal and verifiable example for it.
The first file is in charge of dealing with the virtual machine
#include <stdlib.h>
#include <stdint.h>
typedef int32_t value_t;
typedef enum {
Lb, Lb1, Lb2, Lb3, Lb4, Lb5,
Ib, Ob
} reg_bank_t;
static value_t* memory_start;
static value_t* R[8];
value_t* engine_get_Lb(void) { return R[Lb]; }
value_t engine_run() {
memory_start = memory_get_start();
for (reg_bank_t pseudo_bank = Lb; pseudo_bank <= Lb5; ++pseudo_bank)
R[pseudo_bank] = memory_start + (pseudo_bank - Lb) * 32;
value_t* block = memory_allocate();
}
Then I have the actual garbage collector, the minimized code is:
#include <stdlib.h>
#include <stdint.h>
typedef int32_t value_t;
static value_t* memory_start = NULL;
void memory_setup(size_t total_byte_size) {
memory_start = calloc(total_byte_size, 1);
}
void* memory_get_start() { return memory_start; }
void mark(value_t* base){
value_t vbase = 0;
}
value_t* memory_allocate() {
mark(engine_get_Lb());
return engine_get_Lb();
}
Finally, minimal main is:
int main(int argc, char* argv[]) {
memory_setup(1000000);
engine_run();
return 0;
}
The problem I'm getting with gdb is that if I print engine_get_Lb() I get the address (value_t *) 0x7ffff490a800 while when printing base inside of the function mark I get the address (value_t *) 0xfffffffff490a800.
Any idea why this is happening?
Complementary files that may help
The makefile
SHELL=/bin/bash
SRCS=src/engine.c \
src/main.c \
src/memory_mark_n_sweep.c
CFLAGS_COMMON=-std=c11 -fwrapv
CLANG_SAN_FLAGS=-fsanitize=address
# Clang warning flags
CLANG_WARNING_FLAGS=-Weverything \
-Wno-format-nonliteral \
-Wno-c++98-compat \
-Wno-gnu-label-as-value
# Flags for debugging:
CFLAGS_DEBUG=${CFLAGS_COMMON} -g ${CLANG_SAN_FLAGS} ${CLANG_WARNING_FLAGS}
# Flags for maximum performance:
CFLAGS_RELEASE=${CFLAGS_COMMON} -O3 -DNDEBUG
CFLAGS=${CFLAGS_DEBUG}
all: vm
vm: ${SRCS}
mkdir -p bin
clang ${CFLAGS} ${LDFLAGS} ${SRCS} -o bin/vm
File with instructions .asm
5c190000 RALO(Lb,25)

Answer 1

value_t* memory_allocate() {
mark(engine_get_Lb());
return engine_get_Lb();
}
engine_get_Lb is not declared before use. It is assumed by the compiler to return int, per an antiquated and dangerous rule of the C language. It was deprecated in the C standard for quite some time, and now is finally removed.
Create a header file with declarations of all your global functions, and #include it in all your source files.
Your compiler should have at least warned you about this error at its default settings. If it did, you should have read and completely understood the warnings before continuing. If it didn't, consider an upgrade. If you cannot upgrade, permanently add -Wall -Wextra -Werror to your compilation flags. Consider also -Wpedantic and -std=c11.