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Fix printf-family functions on long double inf (#1273)

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Cosmopolitan's printf-family functions currently very poorly handle
being passed a long double infinity.

For instance, a program such as:

```cpp
#include <stdio.h>

int main()
{
    printf("%f\n", 1.0 / 0.0);
    printf("%Lf\n", 1.0L / 0.0L);
    printf("%e\n", 1.0 / 0.0);
    printf("%Le\n", 1.0L / 0.0L);
    printf("%g\n", 1.0 / 0.0);
    printf("%Lg\n", 1.0L / 0.0L);
}
```

will currently output the following:

```
inf
0.000000[followed by 32763 more zeros]
inf
N.aN0000e-32769
inf
N.aNe-32769
```

when the correct expected output would be:

```
inf
inf
inf
inf
inf
inf
```

This patch fixes this, and adds tests for the behavior.
This commit is contained in:
Gabriel Ravier 2024-09-01 22:10:48 +02:00 committed by GitHub
parent cca0edd62b
commit 75e161b27b
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
2 changed files with 44 additions and 8 deletions
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16
libc/stdio/fmt.c
View file

@ -615,7 +615,7 @@ static void __fmt_ldfpbits(union U *u, struct FPBits *b) {
#if LDBL_MANT_DIG == 113
b->bits[3] |= 1 << (112 - 32 * 3); // set lowest exponent bit
#endif
} else if (b->bits[0] | b->bits[1] | b->bits[2] | b->bits[3]) {
} else if (isnan(u->ld)) {
i = STRTOG_NaN;
} else {
i = STRTOG_Infinite;
@ -1145,8 +1145,8 @@ int __fmt(void *fn, void *arg, const char *format, va_list va, int *wrote) {
s = s0 =
gdtoa(fpb.fpi, fpb.ex, fpb.bits, &fpb.kind, 3, prec, &decpt, &se);
}
if (decpt == 9999) {
Format9999:
if (decpt == 9999 || decpt == -32768) {
FormatDecpt9999Or32768:
if (s0)
freedtoa(s0);
bzero(special, sizeof(special));
@ -1258,8 +1258,8 @@ int __fmt(void *fn, void *arg, const char *format, va_list va, int *wrote) {
s = s0 = gdtoa(fpb.fpi, fpb.ex, fpb.bits, &fpb.kind, prec ? 2 : 0,
prec, &decpt, &se);
}
if (decpt == 9999)
goto Format9999;
if (decpt == 9999 || decpt == -32768)
goto FormatDecpt9999Or32768;
c = se - s;
prec1 = prec;
if (!prec) {
@ -1304,8 +1304,8 @@ int __fmt(void *fn, void *arg, const char *format, va_list va, int *wrote) {
s = s0 = gdtoa(fpb.fpi, fpb.ex, fpb.bits, &fpb.kind, prec ? 2 : 0,
prec, &decpt, &se);
}
if (decpt == 9999)
goto Format9999;
if (decpt == 9999 || decpt == -32768)
goto FormatDecpt9999Or32768;
FormatExpo:
if (fpb.sign /* && (x || sign) */)
sign = '-';
@ -1386,7 +1386,7 @@ int __fmt(void *fn, void *arg, const char *format, va_list va, int *wrote) {
}
if (fpb.kind == STRTOG_Infinite || fpb.kind == STRTOG_NaN) {
s0 = 0;
goto Format9999;
goto FormatDecpt9999Or32768;
}
prec1 = __fmt_fpiprec(&fpb);
if ((flags & FLAGS_PRECISION) && prec < prec1) {

36
test/libc/stdio/snprintf_test.c
View file

@ -35,3 +35,39 @@ TEST(snprintf, testPlusFlagOnChar) {
ASSERT_EQ(i, 1);
ASSERT_STREQ(buf, "=");
}
TEST(snprintf, testInf) {
char buf[10] = {};
int i = snprintf(buf, sizeof(buf), "%f", 1.0 / 0.0);
ASSERT_EQ(i, 3);
ASSERT_STREQ(buf, "inf");
memset(buf, 0, 4);
i = snprintf(buf, sizeof(buf), "%Lf", 1.0L / 0.0L);
ASSERT_EQ(i, 3);
ASSERT_STREQ(buf, "inf");
memset(buf, 0, 4);
i = snprintf(buf, sizeof(buf), "%e", 1.0 / 0.0);
ASSERT_EQ(i, 3);
ASSERT_STREQ(buf, "inf");
memset(buf, 0, 4);
i = snprintf(buf, sizeof(buf), "%Le", 1.0L / 0.0L);
ASSERT_EQ(i, 3);
ASSERT_STREQ(buf, "inf");
memset(buf, 0, 4);
i = snprintf(buf, sizeof(buf), "%g", 1.0 / 0.0);
ASSERT_EQ(i, 3);
ASSERT_STREQ(buf, "inf");
memset(buf, 0, 4);
i = snprintf(buf, sizeof(buf), "%Lg", 1.0L / 0.0L);
ASSERT_EQ(i, 3);
ASSERT_STREQ(buf, "inf");
for (i = 4; i < 10; ++i)
ASSERT_EQ(buf[i], '\0');
}