logging: 32 bit float values don't work.

[deadsy]

Code

float x = 1.234f;
printf("this is a 32 bit float %f\n", x);
LOG_INF("this is a 32 bit float %f", x);

Output

***** Booting Zephyr OS build v2.0.0-rc1-50-g70640334730b *****
....
this is a 32 bit float 1.234000
[00:00:00.008,000] ggm.main: this is a 32 bit float 0.000000

Notes
CONFIG_LOG_ENABLE_FANCY_OUTPUT_FORMATTING=y
This uses the minimal libc print formatter for the log messages. The print formatter works for float formatting when invoked via printf, suggesting that the float value is somehow being clobbered in the log functions.

Environment

• OS: Linux
• Toolchain: gcc-arm-none-eabi-8-2018-q4-major
• Board: mimxrt1020_evk

[pabigot]

A summary of the analysis only; I'd prefer @nordic-krch take on this task as it appears to be complex.

The path this code takes through the logging system involves counting the number of arguments and caching one log_arg_t value for each one in an array, then reconstructing the original call stack in the output context.

The count is a simple scan for the number of conversion specifiers. It does not take into account length modifiers or the specifier character itself, and so is incorrect when any given argument exceeds the size of log_arg_t on the target, as is the case with %f and %llu on 32-bit hosts. Any conversions that follow the oversized conversion will also be incorrect.

A fix requires an analysis of the format string to determine the number of log_arg_t values required for each conversion. This analysis will be specific to the selected back-end formatter (either z_prf() or z_vprintk()) and any Kconfig symbols that control the behavior of that formatter.

[dleach02]

Removing 2.1 milestone

[github-actions]

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[koffes]

This is still an issue.
The following example has been compiled with:
CONFIG_NEWLIB_LIBC_FLOAT_PRINTF=y
CONFIG_NEWLIB_LIBC=y

float32_t val = 1.2345;
char buf[25];
sprintf(buf, "sprintf %f", val);
LOG_WRN("%s", log_strdup(buf)); //Yields: "sprintf 1.234500"
printk("printk %f\n", val); //Yields: "printk %f"
printf("printf %f\n", val); //Yields: "printf 1.234500" 
LOG_WRN("LOG_WRN %f", val); //Yields: "LOG_WRN %f"

If these configs are enabled the system should be able to print floating point numbers regardless of print method, If this is not feasible/desirable, there should be some ASSERT or warning when using %f or %e.

[koffes]

@carlescufi can this issue be reopened?

[pabigot]

Yes. It shouldn't have been closed.

[pabigot]

The count is a simple scan for the number of conversion specifiers. It does not take into account length modifiers or the specifier character itself, and so is incorrect when any given argument exceeds the size of log_arg_t

This is something that might be addressed if we build a fully-functional Zephyr API for printf-style formatting with stream output, which is the subject of #29203 (comment).

[pabigot]

With cbprintf_arglen it should now be possible to fix this and all the other bugs related to passing 64-bit values for log formatting. @nordic-krch @carlescufi

[nordic-krch]

@pabigot noted, i will take a look at that.

[github-actions]

This issue has been marked as stale because it has been open (more than) 60 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this issue will automatically be closed in 14 days. Note, that you can always re-open a closed issue at any time.

[deadsy]

I'm running zephyr 2.4.0.
It still doesn't work.

[nordic-krch]

yes, it will be addressed soon, see #30353.

[github-actions]

This issue has been marked as stale because it has been open (more than) 60 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this issue will automatically be closed in 14 days. Note, that you can always re-open a closed issue at any time.

[nordic-krch]

floats can now be logged with new logging. Currently legacy version is the default one, so it has to be explicitly enabled (CONFIG_LOG2_MODE_DEFERRED).

[manoj153]

floats can now be logged with new logging. Currently legacy version is the default one, so it has to be explicitly enabled (CONFIG_LOG2_MODE_DEFERRED).

hi have tried setting CONFIG_LOG2_MODE_DEFERRED=y with the latest zephyr build and yet to print float types,
%f, is just printing out as "%f" , instead of given variable's value so if this makes sense this issue has to be re-open I think

[nordic-krch]

@manoj153 please check if float formatting is enabled in cbprintf CBPRINTF_FP_SUPPORT.

[manoj153]

CBPRINTF_FP_SUPPORT

yes that helps. works now