filters: fix option parsing on arm cpus

When running colorize or wrap on ARM, both programs exit immediately
displaying their help message whatever the provided arguments. This is
caused by an implicit downcast of the getopt return value.

On most architectures, char is signed by default. On ARM, char is
unsigned for performance reasons. Since the signed int return value of
getopt is forced into a char, the results differ on ARM compared to x86.

* Add -Wconversion -Warith-conversion to CFLAGS in CI builds to ensure
  catching such issues in the future.

* Fix all -Wconversion -Warith-conversion reported issues.

* Wide char functions need to deal with wint_t and wchar_t and it is
  guaranteed that a wchar_t can always fit into a wint_t. Add explicit
  casts to silence the reported warnings.

Link: https://www.arm.linux.org.uk/docs/faqs/signedchar.php
Link: https://lwn.net/Articles/911914/
Fixes: https://todo.sr.ht/~rjarry/aerc/164
Reported-by: Bence Ferdinandy <bence@ferdinandy.com>
Suggested-by: Allen Sobot <chilledfrogs@disroot.org>
Signed-off-by: Robin Jarry <robin@jarry.cc>
Tested-by: Bence Ferdinandy <bence@ferdinandy.com>

3 files changed, 40 insertions, 37 deletions

diff --git a/.builds/alpine-edge.yml b/.builds/alpine-edge.yml
index 0f097c53..9433a808 100644
--- a/.builds/alpine-edge.yml
+++ b/.builds/alpine-edge.yml
@@ -12,7 +12,7 @@ environment:
   DESTDIR: ./out
   GOFLAGS: "-tags=notmuch"
   CC: gcc
-  CFLAGS: -O2 -g -Wall -Wextra -Werror -Wformat-security -Wstack-protector -fstack-protector-strong -fanalyzer
+  CFLAGS: -O2 -g -Wall -Wextra -Wconversion -Warith-conversion -Werror -Wformat-security -Wstack-protector -fstack-protector-strong -fanalyzer
   FILTERS_TEST_PREFIX: valgrind --leak-check=full --error-exitcode=1
 tasks:
   - lint: |
diff --git a/filters/colorize.c b/filters/colorize.c
index 5122b241..1c979d11 100644
--- a/filters/colorize.c
+++ b/filters/colorize.c
@@ -472,8 +472,8 @@ static void urls(const char *in, struct style *ctx)
 	bool trim;
 
 	while (!regexec(&url_re, in, 3, groups, 0)) {
-		in += print_notabs(in, groups[0].rm_so);
-		len = groups[0].rm_eo - groups[0].rm_so;
+		in += print_notabs(in, (size_t)groups[0].rm_so);
+		len = (size_t)groups[0].rm_eo - (size_t)groups[0].rm_so;
 
 		if (groups[1].rm_so != -1) {
 			/* Standard URL (i.e. not mailto: nor email address).
@@ -565,7 +565,7 @@ static void header(const char *in)
 
 	if (!regexec(&header_re, in, 1, groups, 0)) {
 		print(seq(&styles.header));
-		in += print_notabs(in, groups[0].rm_eo);
+		in += print_notabs(in, (size_t)groups[0].rm_eo);
 		print(RESET);
 	}
 	urls(in, NULL);
@@ -580,7 +580,7 @@ static void quote(const char *in)
 {
 	regmatch_t groups[8];
 	struct style *s;
-	int q, level;
+	size_t q, level;
 
 	q = level = 0;
 	while (in[q] == '>') {
@@ -704,7 +704,7 @@ static void colorize_line(const char *in)
 int parse_args(int argc, char **argv)
 {
 	const char *filename = NULL;
-	char c;
+	int c;
 
 	styleset = getenv("AERC_STYLESET");
 
diff --git a/filters/wrap.c b/filters/wrap.c
index 5f5279c8..e6c73057 100644
--- a/filters/wrap.c
+++ b/filters/wrap.c
@@ -29,14 +29,15 @@ static void usage(void)
 }
 
 static size_t margin = 80;
-static long prose_ratio = 50;
+static size_t prose_ratio = 50;
 static bool reflow;
 static FILE *in_file;
 
 int parse_args(int argc, char **argv)
 {
 	const char *filename = NULL;
-	char c;
+	long value;
+	int c;
 
 	while ((c = getopt(argc, argv, "hrw:l:f:")) != -1) {
 		errno = 0;
@@ -45,26 +46,28 @@ int parse_args(int argc, char **argv)
 			reflow = true;
 			break;
 		case 'l':
-			prose_ratio = strtol(optarg, NULL, 10);
+			value = strtol(optarg, NULL, 10);
 			if (errno) {
 				perror("error: invalid ratio value");
 				return 1;
 			}
-			if (prose_ratio <= 0 || prose_ratio >= 100) {
+			if (value <= 0 || value >= 100) {
 				fprintf(stderr, "error: ratio must be ]0,100[\n");
 				return 1;
 			}
+			prose_ratio = (size_t)value;
 			break;
 		case 'w':
-			margin = strtol(optarg, NULL, 10);
+			value = strtol(optarg, NULL, 10);
 			if (errno) {
 				perror("error: invalid width value");
 				return 1;
 			}
-			if (margin < 1) {
+			if (value < 1) {
 				fprintf(stderr, "error: width must be positive\n");
 				return 1;
 			}
+			margin = (size_t)value;
 			break;
 		case 'f':
 			filename = optarg;
@@ -95,7 +98,7 @@ int parse_args(int argc, char **argv)
 static bool is_empty(const wchar_t *s)
 {
 	while (*s != L'\0') {
-		if (!iswspace(*s++))
+		if (!iswspace((wint_t)*s++))
 			return false;
 	}
 	return true;
@@ -131,7 +134,7 @@ struct paragraph {
 	/* actual text of this paragraph */
 	wchar_t *text;
 	/* percentage of letters in text */
-	int prose_ratio;
+	size_t prose_ratio;
 	/* text ends with a space */
 	bool flowed;
 	/* paragraph is a list item */
@@ -164,27 +167,27 @@ static size_t list_item_offset(const wchar_t *buf)
 	if (buf[i] == L'-' || buf[i] == '*' || buf[i] == '.') {
 		/* bullet list */
 		i++;
-	} else if (iswdigit(buf[i])) {
+	} else if (iswdigit((wint_t)buf[i])) {
 		/* numbered list */
 		i++;
-		if (iswdigit(buf[i])) {
+		if (iswdigit((wint_t)buf[i])) {
 			i++;
 		}
-	} else if (iswalpha(buf[i])) {
+	} else if (iswalpha((wint_t)buf[i])) {
 		/* lettered list */
-		c = towlower(buf[i]);
+		c = (wchar_t)towlower((wint_t)buf[i]);
 		i++;
 		if (c == L'i' || c == L'v') {
 			/* roman i. ii. iii. iv. ... */
-			c = towlower(buf[i]);
+			c = (wchar_t)towlower((wint_t)buf[i]);
 			while (i < 4 && (c == L'i' || c == L'v')) {
-				c = towlower(buf[++i]);
+				c = (wchar_t)towlower((wint_t)buf[++i]);
 			}
 		}
 	} else {
 		return 0;
 	}
-	if (iswdigit(buf[0]) || iswalpha(buf[0])) {
+	if (iswdigit((wint_t)buf[0]) || iswalpha((wint_t)buf[0])) {
 		if (buf[i] == L')' || buf[i] == L'/' || buf[i] == L'.') {
 			i++;
 		} else {
@@ -228,13 +231,13 @@ static struct paragraph *parse_line(const wchar_t *buf)
 	}
 	/* detect list item prefix & indent */
 	t = q;
-	while (iswspace(buf[t])) {
+	while (iswspace((wint_t)buf[t])) {
 		t++;
 	}
 	i = list_item_offset(&buf[t]);
 	list_item = i != 0;
 	t += i;
-	while (iswspace(buf[t])) {
+	while (iswspace((wint_t)buf[t])) {
 		t++;
 	}
 	indent_len = t - q;
@@ -242,14 +245,14 @@ static struct paragraph *parse_line(const wchar_t *buf)
 	e = t;
 	letters = 0;
 	while (buf[e] != L'\0') {
-		if (iswalpha(buf[e++])) {
+		if (iswalpha((wint_t)buf[e++])) {
 			letters++;
 		}
 	}
 	/* strip trailing whitespace unless it is a signature delimiter */
 	flowed = false;
 	if (wcscmp(&buf[q], L"-- ") != 0) {
-		while (e > q && iswspace(buf[e - 1])) {
+		while (e > q && iswspace((wint_t)buf[e - 1])) {
 			e--;
 			flowed = true;
 		}
@@ -311,7 +314,7 @@ static void join_paragraph(
 	wchar_t *text;
 
 	/* trim leading whitespace of the next paragraph before joining */
-	while (*append != L'\0' && iswspace(*append))
+	while (*append != L'\0' && iswspace((wint_t)*append))
 		append++;
 
 	len = wcslen(p->text);
@@ -342,8 +345,8 @@ static void join_paragraph(
  */
 static void write_paragraph(struct paragraph *p)
 {
-	size_t quotes_width = wcswidth(p->quotes, wcslen(p->quotes));
-	size_t remain = wcswidth(p->text, wcslen(p->text));
+	size_t quotes_width = (size_t)wcswidth(p->quotes, wcslen(p->quotes));
+	size_t remain = (size_t)wcswidth(p->text, wcslen(p->text));
 	const wchar_t *indent = L"";
 	wchar_t *text = p->text;
 	bool more = true;
@@ -351,7 +354,7 @@ static void write_paragraph(struct paragraph *p)
 	size_t width;
 
 	while (more) {
-		width = quotes_width + wcswidth(indent, wcslen(indent));
+		width = quotes_width + (size_t)wcswidth(indent, wcslen(indent));
 
 		if (width + remain <= margin || p->prose_ratio < prose_ratio) {
 			/* whole paragraph fits on a single line */
@@ -359,18 +362,18 @@ static void write_paragraph(struct paragraph *p)
 			more = false;
 		} else {
 			/* find split point, preferably before margin */
-			int split = -1;
-			int w = 0;
-			for (int i = 0; text[i] != L'\0'; i++) {
-				w += wcwidth(text[i]);
-				if (width + w > margin && split != -1) {
+			size_t split = -1U;
+			size_t w = 0;
+			for (size_t i = 0; text[i] != L'\0'; i++) {
+				w += (size_t)wcwidth(text[i]);
+				if (width + w > margin && split != -1U) {
 					break;
 				}
-				if (iswspace(text[i])) {
+				if (iswspace((wint_t)text[i])) {
 					split = i;
 				}
 			}
-			if (split == -1) {
+			if (split == -1U) {
 				/* no space found to split, print a long line */
 				line = text;
 				more = false;
@@ -379,7 +382,7 @@ static void write_paragraph(struct paragraph *p)
 				line = text;
 				split++;
 				/* find start of next word */
-				while (iswspace(text[split])) {
+				while (iswspace((wint_t)text[split])) {
 					split++;
 				}
 				if (text[split] != L'\0') {