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Fix MSVC /W4 unreachable-code error in v3 C dtoa

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When TG3JSON_USE_STDLIB_FPCONV is enabled (auto-selected on MSVC), the
stdlib float-formatting block in tg3json__dtoa_c() always returns, making
the manual long-double formatting fallback dead code. MSVC /W4 /WX turned
the resulting C4702 (unreachable code) into a build error.

Make the manual fallback an #else branch of the stdlib path so neither
configuration contains unreachable code, and guard the fallback-only
locals and helpers (tg3json__utoa, tg3json__write_exp,
tg3json__format_decimal_digits) under !TG3JSON_USE_STDLIB_FPCONV to avoid
unused-function/variable warnings on the stdlib path.

Verified with gcc -Wall -Wextra -Werror across all v3 C test sources in
both fpconv configurations, plus runtime runs of tester_v3_json_c.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Syoyo Fujita
2026-06-02 21:15:33 +09:00
parent a4b5752b1b
commit fd365dddab
1 changed files with 8 additions and 1 deletions
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9
tinygltf_json_c.h
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@@ -250,6 +250,7 @@ static size_t tg3json__itoa(int64_t value, char *buf) {
return (size_t)(p - buf);
}
#if !TG3JSON_USE_STDLIB_FPCONV
static size_t tg3json__utoa(uint64_t value, char *buf) {
char tmp[32];
size_t n = 0;
@@ -267,6 +268,7 @@ static size_t tg3json__utoa(uint64_t value, char *buf) {
buf[i] = '\0';
return i;
}
#endif /* !TG3JSON_USE_STDLIB_FPCONV */
static uint64_t tg3json__double_bits(double v) {
uint64_t bits = 0;
@@ -433,6 +435,7 @@ static int tg3json__parse_f64_c(const char *start, const char *end, double *out)
#endif
}
#if !TG3JSON_USE_STDLIB_FPCONV
static char *tg3json__write_exp(char *p, int exp10) {
char tmp[16];
size_t n;
@@ -479,6 +482,7 @@ static char *tg3json__format_decimal_digits(char *out, const char *digits,
for (i = 0; i < ndigits; ++i) *p++ = digits[i];
return p;
}
#endif /* !TG3JSON_USE_STDLIB_FPCONV */
static int tg3json__same_f64(double a, double b) {
return tg3json__double_bits(a) == tg3json__double_bits(b);
@@ -579,6 +583,7 @@ static char *tg3json__dtoa_c(double value, char *buf) {
uint64_t bits = tg3json__double_bits(value);
int negative = (int)(bits >> 63);
uint64_t abits = bits & 0x7fffffffffffffffULL;
#if !TG3JSON_USE_STDLIB_FPCONV
long double x;
int dec_e = 0;
char digits[24];
@@ -586,6 +591,7 @@ static char *tg3json__dtoa_c(double value, char *buf) {
int i;
char best[80];
size_t best_len;
#endif
if (tg3json__is_nan_bits(bits)) {
TINYGLTF_JSON_MEMCPY(buf, "nan", 3);
@@ -644,7 +650,7 @@ static char *tg3json__dtoa_c(double value, char *buf) {
TINYGLTF_JSON_MEMCPY(buf, shortest, TINYGLTF_JSON_STRLEN(shortest));
return buf + TINYGLTF_JSON_STRLEN(shortest);
}
#endif
#else
x = negative ? -(long double)value : (long double)value;
while (x >= 1.0e16L) {
@@ -708,6 +714,7 @@ static char *tg3json__dtoa_c(double value, char *buf) {
}
TINYGLTF_JSON_MEMCPY(buf, best, best_len);
return buf + best_len;
#endif
}
typedef struct tg3json__parser {