printf: floating point conversion flags not supported or incorrect #2774
Description
Floating point conversion flags are defined here: https://www.gnu.org/software/libc/manual/html_node/Floating_002dPoint-Conversions.html
Here are a few failing test cases:
Flag to always include a plus or minus sign:
$ printf "%+3.0f\n" 0
+0
$ ./target/debug/coreutils printf "%+3.0f\n" 0
printf: %+: invalid conversion specification
Flag to pad the field with spaces:
$ printf "% 3.0f\n" 1
1
$ ./target/debug/coreutils printf "% 3.0f\n" 1
printf: % : invalid conversion specification
Flag to pad the field with zeros instead of spaces:
$ printf "%03.0f\n" 0
000
$ ./target/debug/coreutils printf "%03.0f\n" 0
0
Combining the + and 0 flags:
$ printf "%0+3.0f\n" 0
+00
$ ./target/debug/coreutils printf "%0+3.0f\n" 0
printf: %0+: invalid conversion specification
Combining the and - flags:
$ printf "% -3.0f\n" 1
1
$ ./target/debug/coreutils printf "% -3.0f\n" 1
printf: % : invalid conversion specification
Discovered this while investigating #2616.