failure to load highly precise floats

[alex-tee]

when you have a struct with only a float field inside and you set the value to 1.55331e-40f and attempt to save it, it works. it gets printed as:

---
fval: 1.55331e-40
...

when you try to load it however it rejects it:

# cyaml-MESSAGE: Load: PUSH[0]: start
# cyaml-MESSAGE: Load: Event: STREAM_START
# cyaml-MESSAGE: Load: Handle state start
# cyaml-MESSAGE: Load: PUSH[1]: in stream
# cyaml-MESSAGE: Load: Event: DOC_START
# cyaml-MESSAGE: Load: Handle state in stream
# cyaml-MESSAGE: Load: PUSH[2]: in doc
# cyaml-MESSAGE: Load: Event: MAPPING_START
# cyaml-MESSAGE: Load: Handle state in doc
# cyaml-MESSAGE: Load: Reading value of type 'MAPPING' (pointer)
# cyaml-MESSAGE: Load: Allocation: 0x5555555c1030 (0 + 4 bytes)
# cyaml-MESSAGE: Load: PUSH[3]: in mapping (key)
# cyaml-MESSAGE: Load: Event: SCALAR
# cyaml-MESSAGE: Load: Handle state in mapping (key)
# cyaml-MESSAGE: Load: [fval]
# cyaml-MESSAGE: Load: Event: SCALAR
# cyaml-MESSAGE: Load: Handle state in mapping (value
# cyaml-MESSAGE: Load: Reading value of type 'FLOAT'
# cyaml-MESSAGE: Load:   <1.55331e-40>
# cyaml-MESSAGE: Free: Top level data: 0x5555555c1030
# cyaml-MESSAGE: Free: Freeing key: fval (at offset: 0)
# cyaml-MESSAGE: Free: Freeing: 0x5555555c1030
Bail out! cyaml-FATAL-WARNING: Load: Backtrace:
Bail out! cyaml-FATAL-WARNING:   in mapping field: fval
# cyaml-MESSAGE: Load: POP[3]: in mapping (key)
# cyaml-MESSAGE: Load: POP[2]: in doc
# cyaml-MESSAGE: Load: POP[1]: in stream
# cyaml-MESSAGE: Load: POP[0]: start

cyaml error: Invalid value

[alex-tee]

with latest master I get the same issue, except the error is a bit more user friendly: cyaml-WARNING **: 16:57:44.402: Load: Invalid FLOAT value: 1.55331e-40

[alex-tee]

It seems that those values are outside the bounds allowed by floats, but C allows you to save them in float variables anyway. so this could be seen as a user error - I'm passing bad values. but my program receives some values from other libraries and from the user and I still don't want it to break when trying to load these values back.

so I tried this and it fixes my problem:

diff --git a/src/save.c b/src/save.c
index 52ff1f4..7c47c23 100644
--- a/src/save.c
+++ b/src/save.c
@@ -16,6 +16,7 @@
 #include <stdbool.h>
 #include <assert.h>
 #include <limits.h>
+#include <float.h>
 
 #include <yaml.h>
 
@@ -552,6 +553,15 @@ static const char * cyaml__get_float(
 {
        static char string[64];
 
+  /* clamp */
+  if (value <= FLT_MIN)
+    {
+      value = 1e-37;
+    }
+  else if (value >= FLT_MAX)
+    {
+      value = 1e+37;
+    }
        sprintf(string, "%g", value);
 
        return string;

maybe you can do it in a more tidy way unless you have a better solution.

I think since cyaml allows you to save such a value, it should also not have a problem loading it back. my suggestion is to just log a warning that the value was out of bounds and clamp it like above

EDIT: I guess you could just use strtod() instead of strtof() when loading, that would probably make more sense, and do a (float) cast on it

[alex-tee]

another idea is to allow user overrides or callbacks before saving so I could clamp the value in my struct (or do any other arbitrary validation): #120

[tlsa]

Please test with #151

The old behavior of rejecting floating point values that overflow or underflow can be achieved by setting CYAML_FLAG_STRICT.

[alex-tee]

just tried it, this fixes the issue. thanks!

[tlsa]

Thanks, merged.