diff --git a/include/asm/symbol.h b/include/asm/symbol.h
index edef3238..ed49fc78 100644
--- a/include/asm/symbol.h
+++ b/include/asm/symbol.h
@@ -75,7 +75,7 @@ static inline bool sym_IsConstant(struct Symbol const *sym)
 	if (sym->type == SYM_LABEL) {
 		struct Section const *sect = sym_GetSection(sym);
 
-		return sect && sect->org != -1;
+		return sect && sect->org != (uint32_t)-1;
 	}
 	return sym->type == SYM_EQU || sym->type == SYM_SET;
 }
diff --git a/include/link/section.h b/include/link/section.h
index d9da1a5b..dea0889a 100644
--- a/include/link/section.h
+++ b/include/link/section.h
@@ -30,11 +30,11 @@ struct AttachedSymbol {
 struct Patch {
 	struct FileStackNode const *src;
 	uint32_t lineNo;
-	int32_t offset;
+	uint32_t offset;
 	uint32_t pcSectionID;
 	uint32_t pcOffset;
 	enum PatchType type;
-	int32_t rpnSize;
+	uint32_t rpnSize;
 	uint8_t *rpnExpression;
 
 	struct Section const *pcSection;
diff --git a/src/asm/fstack.c b/src/asm/fstack.c
index c04950b7..c85ffb5c 100644
--- a/src/asm/fstack.c
+++ b/src/asm/fstack.c
@@ -175,8 +175,14 @@ bool fstk_FindFile(char const *path, char **fullPath, size_t *size)
 			char const *incPath = i ? includePaths[i - 1] : "";
 			int len = snprintf(*fullPath, *size, "%s%s", incPath, path);
 
+			if (len < 0) {
+				error("snprintf error during include path search: %s\n",
+				      strerror(errno));
+				break;
+			}
+
 			/* Oh how I wish `asnprintf` was standard... */
-			if (len >= *size) { /* `len` doesn't include the terminator, `size` does */
+			if ((size_t)len >= *size) { /* `len` doesn't include the terminator, `size` does */
 				*size = len + 1;
 				*fullPath = realloc(*fullPath, *size);
 				if (!*fullPath) {
@@ -187,10 +193,7 @@ bool fstk_FindFile(char const *path, char **fullPath, size_t *size)
 				len = sprintf(*fullPath, "%s%s", incPath, path);
 			}
 
-			if (len < 0) {
-				error("snprintf error during include path search: %s\n",
-				      strerror(errno));
-			} else if (isPathValid(*fullPath)) {
+			if (isPathValid(*fullPath)) {
 				printDep(*fullPath);
 				return true;
 			}
diff --git a/src/asm/lexer.c b/src/asm/lexer.c
index 50d4d917..97d5d6cf 100644
--- a/src/asm/lexer.c
+++ b/src/asm/lexer.c
@@ -866,8 +866,9 @@ static int peekInternal(uint8_t distance)
 			size_t nbExpectedChars = LEXER_BUF_SIZE - writeIndex;
 
 			readChars(nbExpectedChars);
-			/* If the read was incomplete, don't perform a second read */
-			if (nbCharsRead < nbExpectedChars)
+			// If the read was incomplete, don't perform a second read
+			// `nbCharsRead` cannot be negative, so it's fine to cast to `size_t`
+			if ((size_t)nbCharsRead < nbExpectedChars)
 				target = 0;
 		}
 		if (target != 0)
@@ -2258,7 +2259,7 @@ static int skipIfBlock(bool toEndc)
 {
 	dbgPrint("Skipping IF block (toEndc = %s)\n", toEndc ? "true" : "false");
 	lexer_SetMode(LEXER_NORMAL);
-	int startingDepth = lexer_GetIFDepth();
+	uint32_t startingDepth = lexer_GetIFDepth();
 	int token;
 	bool atLineStart = lexerState->atLineStart;
 
diff --git a/src/asm/macro.c b/src/asm/macro.c
index 8ffddb48..9d642a51 100644
--- a/src/asm/macro.c
+++ b/src/asm/macro.c
@@ -170,12 +170,12 @@ void macro_ShiftCurrentArgs(int32_t count)
 {
 	if (!macroArgs) {
 		error("Cannot shift macro arguments outside of a macro\n");
-	} else if (count > 0 && (count > macroArgs->nbArgs
+	} else if (count > 0 && ((uint32_t)count > macroArgs->nbArgs
 		   || macroArgs->shift > macroArgs->nbArgs - count)) {
 		warning(WARNING_MACRO_SHIFT,
 			"Cannot shift macro arguments past their end\n");
 		macroArgs->shift = macroArgs->nbArgs;
-	} else if (count < 0 && macroArgs->shift < -count) {
+	} else if (count < 0 && macroArgs->shift < (uint32_t)-count) {
 		warning(WARNING_MACRO_SHIFT,
 			"Cannot shift macro arguments past their beginning\n");
 		macroArgs->shift = 0;
diff --git a/src/asm/output.c b/src/asm/output.c
index 37895745..d57c6768 100644
--- a/src/asm/output.c
+++ b/src/asm/output.c
@@ -136,9 +136,9 @@ static uint32_t getNbFileStackNodes(void)
 void out_RegisterNode(struct FileStackNode *node)
 {
 	/* If node is not already registered, register it (and parents), and give it a unique ID */
-	while (node->ID == -1) {
+	while (node->ID == (uint32_t)-1) {
 		node->ID = getNbFileStackNodes();
-		if (node->ID == -1)
+		if (node->ID == (uint32_t)-1)
 			fatalerror("Reached too many file stack nodes; try splitting the file up\n");
 		node->next = fileStackNodes;
 		fileStackNodes = node;
@@ -266,7 +266,7 @@ static void registerSymbol(struct Symbol *sym)
 	*objectSymbolsTail = sym;
 	objectSymbolsTail = &sym->next;
 	out_RegisterNode(sym->src);
-	if (nbSymbols == -1)
+	if (nbSymbols == (uint32_t)-1)
 		fatalerror("Registered too many symbols (%" PRIu32
 			   "); try splitting up your files\n", (uint32_t)-1);
 	sym->ID = nbSymbols++;
@@ -278,7 +278,7 @@ static void registerSymbol(struct Symbol *sym)
  */
 static uint32_t getSymbolID(struct Symbol *sym)
 {
-	if (sym->ID == -1 && !sym_IsPC(sym))
+	if (sym->ID == (uint32_t)-1 && !sym_IsPC(sym))
 		registerSymbol(sym);
 	return sym->ID;
 }
@@ -474,7 +474,7 @@ static void registerUnregisteredSymbol(struct Symbol *symbol, void *arg)
 	(void)arg; // sym_ForEach requires a void* parameter, but we are not using it.
 
 	// Check for symbol->src, to skip any built-in symbol from rgbasm
-	if (symbol->src && symbol->ID == -1) {
+	if (symbol->src && symbol->ID == (uint32_t)-1) {
 		registerSymbol(symbol);
 	}
 }
diff --git a/src/asm/parser.y b/src/asm/parser.y
index 30a08c41..24411a07 100644
--- a/src/asm/parser.y
+++ b/src/asm/parser.y
@@ -176,7 +176,9 @@ static void strrpl(char *dest, size_t destLen, char const *src, char const *old,
 
 	for (char const *next = strstr(src, old); next && *next; next = strstr(src, old)) {
 		// Copy anything before the substring to replace
-		memcpy(dest + i, src, next - src < destLen - i ? next - src : destLen - i);
+		unsigned int lenBefore = next - src;
+
+		memcpy(dest + i, src, lenBefore < destLen - i ? lenBefore : destLen - i);
 		i += next - src;
 		if (i >= destLen)
 			break;
@@ -1437,7 +1439,11 @@ string		: T_STRING
 
 strcat_args	: string
 		| strcat_args T_COMMA string {
-			if (snprintf($$, sizeof($$), "%s%s", $1, $3) >= sizeof($$))
+			int ret = snprintf($$, sizeof($$), "%s%s", $1, $3);
+
+			if (ret == -1)
+				fatalerror("snprintf error in STRCAT: %s\n", strerror(errno));
+			else if ((unsigned int)ret >= sizeof($$))
 				warning(WARNING_LONG_STR, "STRCAT: String too long '%s%s'\n",
 					$1, $3);
 		}
diff --git a/src/asm/rpn.c b/src/asm/rpn.c
index 3abd7ad9..bc363c17 100644
--- a/src/asm/rpn.c
+++ b/src/asm/rpn.c
@@ -139,7 +139,7 @@ void rpn_BankSelf(struct Expression *expr)
 	if (!pCurrentSection) {
 		error("PC has no bank outside a section\n");
 		expr->nVal = 1;
-	} else if (pCurrentSection->bank == -1) {
+	} else if (pCurrentSection->bank == (uint32_t)-1) {
 		makeUnknown(expr, "Current section's bank is not known");
 		expr->nRPNPatchSize++;
 		*reserveSpace(expr, 1) = RPN_BANK_SELF;
@@ -165,7 +165,7 @@ void rpn_BankSymbol(struct Expression *expr, char const *tzSym)
 		sym = sym_Ref(tzSym);
 		assert(sym); // If the symbol didn't exist, it should have been created
 
-		if (sym_GetSection(sym) && sym_GetSection(sym)->bank != -1) {
+		if (sym_GetSection(sym) && sym_GetSection(sym)->bank != (uint32_t)-1) {
 			/* Symbol's section is known and bank is fixed */
 			expr->nVal = sym_GetSection(sym)->bank;
 		} else {
@@ -186,7 +186,7 @@ void rpn_BankSection(struct Expression *expr, char const *tzSectionName)
 
 	struct Section *pSection = out_FindSectionByName(tzSectionName);
 
-	if (pSection && pSection->bank != -1) {
+	if (pSection && pSection->bank != (uint32_t)-1) {
 		expr->nVal = pSection->bank;
 	} else {
 		makeUnknown(expr, "Section \"%s\"'s bank is not known",
diff --git a/src/asm/section.c b/src/asm/section.c
index 72557a5d..eb923140 100644
--- a/src/asm/section.c
+++ b/src/asm/section.c
@@ -114,9 +114,9 @@ static unsigned int mergeSectUnion(struct Section *sect, enum SectionType type,
 	if (sect_HasData(type))
 		fail("Cannot declare ROM sections as UNION\n");
 
-	if (org != -1) {
+	if (org != (uint32_t)-1) {
 		/* If both are fixed, they must be the same */
-		if (sect->org != -1 && sect->org != org)
+		if (sect->org != (uint32_t)-1 && sect->org != org)
 			fail("Section already declared as fixed at different address $%04"
 			     PRIx32 "\n", sect->org);
 		else if (sect->align != 0 && (mask(sect->align) & (org - sect->alignOfs)))
@@ -128,7 +128,7 @@ static unsigned int mergeSectUnion(struct Section *sect, enum SectionType type,
 
 	} else if (alignment != 0) {
 		/* Make sure any fixed address given is compatible */
-		if (sect->org != -1) {
+		if (sect->org != (uint32_t)-1) {
 			if ((sect->org - alignOffset) & mask(alignment))
 				fail("Section already declared as fixed at incompatible address $%04"
 				     PRIx32 "\n", sect->org);
@@ -160,11 +160,11 @@ static unsigned int mergeFragments(struct Section *sect, enum SectionType type,
 	 * combination of both.
 	 * The merging is however performed at the *end* of the original section!
 	 */
-	if (org != -1) {
+	if (org != (uint32_t)-1) {
 		uint16_t curOrg = org - sect->size;
 
 		/* If both are fixed, they must be the same */
-		if (sect->org != -1 && sect->org != curOrg)
+		if (sect->org != (uint32_t)-1 && sect->org != curOrg)
 			fail("Section already declared as fixed at incompatible address $%04"
 			     PRIx32 " (cur addr = %04" PRIx32 ")\n",
 			     sect->org, sect->org + sect->size);
@@ -182,7 +182,7 @@ static unsigned int mergeFragments(struct Section *sect, enum SectionType type,
 			curOfs += 1U << alignment;
 
 		/* Make sure any fixed address given is compatible */
-		if (sect->org != -1) {
+		if (sect->org != (uint32_t)-1) {
 			if ((sect->org - curOfs) & mask(alignment))
 				fail("Section already declared as fixed at incompatible address $%04"
 				     PRIx32 "\n", sect->org);
@@ -221,10 +221,10 @@ static void mergeSections(struct Section *sect, enum SectionType type, uint32_t
 			// Common checks
 
 			/* If the section's bank is unspecified, override it */
-			if (sect->bank == -1)
+			if (sect->bank == (uint32_t)-1)
 				sect->bank = bank;
 			/* If both specify a bank, it must be the same one */
-			else if (bank != -1 && sect->bank != bank)
+			else if (bank != (uint32_t)-1 && sect->bank != bank)
 				fail("Section already declared with different bank %" PRIu32 "\n",
 				     sect->bank);
 			break;
@@ -296,7 +296,7 @@ static struct Section *getSection(char const *name, enum SectionType type, uint3
 
 	// First, validate parameters, and normalize them if applicable
 
-	if (bank != -1) {
+	if (bank != (uint32_t)-1) {
 		if (type != SECTTYPE_ROMX && type != SECTTYPE_VRAM
 		 && type != SECTTYPE_SRAM && type != SECTTYPE_WRAMX)
 			error("BANK only allowed for ROMX, WRAMX, SRAM, or VRAM sections\n");
@@ -316,7 +316,7 @@ static struct Section *getSection(char const *name, enum SectionType type, uint3
 		alignOffset = 0;
 	}
 
-	if (org != -1) {
+	if (org != (uint32_t)-1) {
 		if (org < startaddr[type] || org > endaddr(type))
 			error("Section \"%s\"'s fixed address %#" PRIx32
 				" is outside of range [%#" PRIx16 "; %#" PRIx16 "]\n",
@@ -331,7 +331,7 @@ static struct Section *getSection(char const *name, enum SectionType type, uint3
 		/* It doesn't make sense to have both alignment and org set */
 		uint32_t mask = mask(alignment);
 
-		if (org != -1) {
+		if (org != (uint32_t)-1) {
 			if ((org - alignOffset) & mask)
 				error("Section \"%s\"'s fixed address doesn't match its alignment\n",
 					name);
@@ -453,7 +453,7 @@ void sect_AlignPC(uint8_t alignment, uint16_t offset)
 	struct Section *sect = sect_GetSymbolSection();
 	uint16_t alignSize = 1 << alignment; // Size of an aligned "block"
 
-	if (sect->org != -1) {
+	if (sect->org != (uint32_t)-1) {
 		if ((sym_GetPCValue() - offset) % alignSize)
 			error("Section's fixed address fails required alignment (PC = $%04" PRIx32
 			      ")\n", sym_GetPCValue());
diff --git a/src/asm/symbol.c b/src/asm/symbol.c
index 46d140f4..f284b196 100644
--- a/src/asm/symbol.c
+++ b/src/asm/symbol.c
@@ -179,7 +179,7 @@ static void updateSymbolFilename(struct Symbol *sym)
 
 	setSymbolFilename(sym);
 	/* If the old node was referenced, ensure the new one is */
-	if (oldSrc && oldSrc->referenced && oldSrc->ID != -1)
+	if (oldSrc && oldSrc->referenced && oldSrc->ID != (uint32_t)-1)
 		out_RegisterNode(sym->src);
 	/* TODO: unref the old node, and use `out_ReplaceNode` instead if deleting it */
 }
@@ -277,7 +277,7 @@ struct Symbol const *sym_GetPC(void)
 
 static inline bool isReferenced(struct Symbol const *sym)
 {
-	return sym->ID != -1;
+	return sym->ID != (uint32_t)-1;
 }
 
 /*
@@ -315,7 +315,7 @@ uint32_t sym_GetPCValue(void)
 
 	if (!sect)
 		error("PC has no value outside a section\n");
-	else if (sect->org == -1)
+	else if (sect->org == (uint32_t)-1)
 		error("Expected constant PC but section is not fixed\n");
 	else
 		return CallbackPC();
diff --git a/src/asm/util.c b/src/asm/util.c
index 816ce845..ff55a161 100644
--- a/src/asm/util.c
+++ b/src/asm/util.c
@@ -57,7 +57,7 @@ char const *print(int c)
 
 	default: /* Print as hex */
 		buf[1] = 'x';
-		sprintf(&buf[2], "%02hhx", c);
+		sprintf(&buf[2], "%02hhx", (uint8_t)c);
 		return buf;
 	}
 	buf[2] = '\0';
diff --git a/src/fix/main.c b/src/fix/main.c
index 2ae2cdb9..35cfb5c1 100644
--- a/src/fix/main.c
+++ b/src/fix/main.c
@@ -870,11 +870,13 @@ static void processFile(int input, int output, char const *name, off_t fileSize)
 
 	// Output ROMX if it was buffered
 	if (romx) {
+		// The value returned is either -1, or smaller than `totalRomxLen`,
+		// so it's fine to cast to `size_t`
 		writeLen = writeBytes(output, romx, totalRomxLen);
 		if (writeLen == -1) {
 			report("FATAL: Failed to write \"%s\"'s ROMX: %s\n", name, strerror(errno));
 			goto free_romx;
-		} else if (writeLen < totalRomxLen) {
+		} else if ((size_t)writeLen < totalRomxLen) {
 			report("FATAL: Could only write %ld of \"%s\"'s %ld ROMX bytes\n",
 			       writeLen, name, totalRomxLen);
 			goto free_romx;
@@ -898,7 +900,9 @@ static void processFile(int input, int output, char const *name, off_t fileSize)
 			size_t thisLen = len > sizeof(bank) ? sizeof(bank) : len;
 			ssize_t ret = writeBytes(output, bank, thisLen);
 
-			if (ret != thisLen) {
+			// The return value is either -1, or at most `thisLen`,
+			// so it's fine to cast to `size_t`
+			if ((size_t)ret != thisLen) {
 				report("FATAL: Failed to write \"%s\"'s padding: %s\n",
 				       name, strerror(errno));
 				break;
diff --git a/src/link/object.c b/src/link/object.c
index 66dca803..91f44b15 100644
--- a/src/link/object.c
+++ b/src/link/object.c
@@ -188,7 +188,7 @@ static void readFileStackNode(FILE *file, struct FileStackNode fileNodes[], uint
 
 	tryReadlong(parentID, file,
 		    "%s: Cannot read node #%" PRIu32 "'s parent ID: %s", fileName, i);
-	fileNodes[i].parent = parentID == -1 ? NULL : &fileNodes[parentID];
+	fileNodes[i].parent = parentID == (uint32_t)-1 ? NULL : &fileNodes[parentID];
 	tryReadlong(fileNodes[i].lineNo, file,
 		    "%s: Cannot read node #%" PRIu32 "'s line number: %s", fileName, i);
 	tryGetc(fileNodes[i].type, file, "%s: Cannot read node #%" PRIu32 "'s type: %s",
@@ -279,7 +279,8 @@ static void readPatch(FILE *file, struct Patch *patch, char const *fileName, cha
 	tryReadlong(patch->pcSectionID, file,
 		    "%s: Unable to read \"%s\"'s patch #%" PRIu32 "'s PC offset: %s",
 		    fileName, sectName, i);
-	patch->pcSection = patch->pcSectionID == -1 ? NULL : fileSections[patch->pcSectionID];
+	patch->pcSection = patch->pcSectionID == (uint32_t)-1 ? NULL
+							      : fileSections[patch->pcSectionID];
 	tryReadlong(patch->pcOffset, file,
 		    "%s: Unable to read \"%s\"'s patch #%" PRIu32 "'s PC offset: %s",
 		    fileName, sectName, i);
@@ -635,7 +636,7 @@ static void freeSection(struct Section *section, void *arg)
 	free(section->name);
 	if (sect_HasData(section->type)) {
 		free(section->data);
-		for (int32_t i = 0; i < section->nbPatches; i++)
+		for (uint32_t i = 0; i < section->nbPatches; i++)
 			free(section->patches[i].rpnExpression);
 		free(section->patches);
 	}