glibc 2.31 build error conflicting types for built-in function 'modfl'

[Chris Packham]

On 27/08/20 7:51 pm, Chris Packham wrote:
> Hi,
>
> I'm not sure if this is a issue or glibc or a gcc issue (or operator 
> error).
>
> We're in the process of adding gcc 10.2.0 to crosstool-ng but the 
> arm-unknown-linux-gnueabi configuration is failing with
>
> [ALL  ]      In file included from <command-line>:
> [ERROR]      ../sysdeps/ieee754/dbl-64/s_modf.c:84:28: error: 
> conflicting types for built-in function 'modfl'; expected 'long 
> double(long double,  long double *)' 
> [-Werror=builtin-declaration-mismatch]
> [ALL  ]         84 | libm_alias_double (__modf, modf)
> [ALL  ]            |                            ^~~~
> [ALL  ]      ./../include/libc-symbols.h:152:26: note: in definition 
> of macro '_weak_alias'
> [ALL  ]        152 |   extern __typeof (name) aliasname __attribute__ 
> ((weak, alias (#name))) | ^~~~~~~~~
> [ALL  ]      ../sysdeps/generic/libm-alias-double.h:61:3: note: in 
> expansion of macro 'weak_alias'
> [ALL  ]         61 |   weak_alias (from ## r, to ## l ## r);        
> |   ^~~~~~~~~~
> [ALL  ]      ../sysdeps/generic/libm-alias-double.h:70:37: note: in 
> expansion of macro 'libm_alias_double_r'
> [ALL  ]         70 | #define libm_alias_double(from, to) 
> libm_alias_double_r (from, to, )
> [ALL  ]            | ^~~~~~~~~~~~~~~~~~~
> [ALL  ]      ../sysdeps/ieee754/dbl-64/s_modf.c:84:1: note: in 
> expansion of macro 'libm_alias_double'
> [ALL  ]         84 | libm_alias_double (__modf, modf)
> [ALL  ]            | ^~~~~~~~~~~~~~~~~
> [ALL  ]      ../sysdeps/ieee754/dbl-64/s_modf.c:25:1: note: 'modfl' is 
> declared in header '<math.h>'
> [ALL  ]         24 | #include <libm-alias-double.h>
> [ALL  ]        +++ |+#include <math.h>
> [ALL  ]         25 |
> [ALL  ]      cc1: all warnings being treated as errors
>
> the same libc builds fine under gcc-9.2.0.
>
> Does this look familiar to anyone?

A bit of searching turned up 
https://sourceware.org/git?p=glibc.git;a=patch;h=49348beafe9ba150c9bd48595b3f372299bddbb0