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Fix printf alternative form+precision+octal bugs

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The C standard states that:
> For o conversion, it increases the precision, if and only if
> necessary, to force the first digit of the result to be a zero (if
> the value and precision are both 0, a single 0 is printed).
- The C standard, 7.23.6.1.6. The fprintf function

When printing numbers in their alternative form, with a precision and
with a conversion specifier of o (octal), Cosmopolitan currently fails
to obey this in two ways:
1. When printing a value with a precision that results in 0-padding,
   cosmopolitan would still add an extra 0 even though this should be
   done "if and only if necessary"
2. When printing a value of 0 with a precision of 0, nothing is
   printed, even though the standard specifically states that a single
   0 is printed in this case

This patch fixes this.
This commit is contained in:
Gabriel Ravier 2023-03-27 21:48:46 +02:00
parent e816e97762
commit 54ed6ad4ac
2 changed files with 12 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

8
libc/fmt/ntoa.c
View file

@ -46,8 +46,8 @@ static int __fmt_ntoa_format(int out(const char *, void *, size_t), void *arg,
}
/* handle hash */
if (flags & FLAGS_HASH) {
if (!(flags & FLAGS_PRECISION) && len &&
((len == prec) || (len == width)) && buf[len - 1] == '0') {
if ((!(flags & FLAGS_PRECISION) || log2base == 3) && len &&
((len >= prec) || (len >= width)) && buf[len - 1] == '0') {
len--;
if (len && (log2base == 4 || log2base == 1) && buf[len - 1] == '0') {
len--;
@ -95,7 +95,9 @@ int __fmt_ntoa2(int out(const char *, void *, size_t), void *arg,
unsigned len, count, digit;
char buf[BUFFER_SIZE];
len = 0;
if (!value) flags &= ~FLAGS_HASH;
/* we check for log2base != 3 because otherwise we'll print nothing for a value of 0 with precision 0 when # mandates that one be printed */
if (!value && log2base != 3)
flags &= ~FLAGS_HASH;
if (value || !(flags & FLAGS_PRECISION)) {
count = 0;
do {

7
test/libc/fmt/fmt_test.c
View file

@ -80,6 +80,13 @@ TEST(fmt, x) {
EXPECT_STREQ("0x00136d ", _gc(xasprintf("%#-010.6x", 4973)));
}
TEST(fmt, o) {
EXPECT_STREQ("0000000000000037777777634", _gc(xasprintf("%#.25o", -100)));
EXPECT_STREQ("0001777777777777777777634", _gc(xasprintf("%#.25lo", -100L)));
EXPECT_STREQ("0001777777777777777777634", _gc(xasprintf("%#.25llo", -100LL)));
EXPECT_STREQ("0", _gc(xasprintf("%#.o", 0)));
}
TEST(fmt, b) {
EXPECT_STREQ("000010100 ", _gc(xasprintf("%-14.9b", 20)));
}