https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109921
Bug ID: 109921
Summary: c++17/floating_from_chars.cc: compile error:
‘from_chars_strtod’ was not declared in this scope
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: br015 at umbiko dot net
Target Milestone: ---
This was observed in 13.1.0, but code is the same as git master. Line numbers
and code snippets refer to git master.
/observed error/
Cross-compiling gcc 13.1 for a system without locales, libstdc++ fails to build
with the following error:
>Making all in c++17
>/bin/bash ../../libtool --tag CXX --tag disable-shared --mode=compile
>/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/./gcc/xgcc
>-shared-libgcc
>-B/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/./gcc
>-nostdinc++
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/src
>
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/src/.libs
>
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/libsupc++/.libs
> -B/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/bin/
>-B/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/lib/ -isystem
>/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/include
>-isystem
>/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/sys-include
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/libstdc++-v3/../libgcc
>
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/include/x86_64-buildroot-linux-uclibc
>
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/include
>
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/libstdc++-v3/libsupc++
> -std=gnu++17 -nostdinc++ -prefer-pic -D_GLIBCXX_SHARED
>-fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual -Wabi=2
>-fdiagnostics-show-location=once -ffunction-sections -fdata-sections
>-frandom-seed=floating_from_chars.lo -fimplicit-templates -D_LARGEFILE_SOURCE
>-D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -g0 -D_GNU_SOURCE
>-fcf-protection -mshstk -c -o floating_from_chars.lo
>../../../../../libstdc++-v3/src/c++17/floating_from_chars.cc
>libtool: compile:
>/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/./gcc/xgcc
>-shared-libgcc
>-B/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/./gcc
>-nostdinc++
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/src
>
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/src/.libs
>
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/libsupc++/.libs
> -B/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/bin/
>-B/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/lib/ -isystem
>/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/include
>-isystem
>/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/sys-include
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/libstdc++-v3/../libgcc
>
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstlibtool:
> compile:
>/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/./gcc/xgcc
>-shared-libgcc
>-B/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/./gcc
>-nostdinc++
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/src
>
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/src/.libs
>
>-L/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/libsupc++/.libs
> -B/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/bin/
>-B/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/lib/ -isystem
>/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/include
>-isystem
>/home/data/buildroot.x86_64/host/x86_64-buildroot-linux-uclibc/sys-include
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/libstdc++-v3/../libgcc
>
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/include/x86_64-buildroot-linux-uclibc
>
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/build/x86_64-buildroot-linux-uclibc/libstdc++-v3/include
>
>-I/home/data/buildroot.x86_64/build/host-gcc-final-13.1.0/libstdc++-v3/libsupc++
> -std=gnu++17 -nostdinc++ -D_GLIBCXX_SHARED -fno-implicit-templates -Wall
>-Wextra -Wwrite-strings -Wcast-qual -Wabi=2 -fdiagnostics-show-location=once
>-ffunction-sections -fdata-sections -frandom-seed=floating_from_chars.lo
>-fimplicit-templates -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
>-D_FILE_OFFSET_BITS=64 -O2 -g0 -D_GNU_SOURCE -fcf-protection -mshstk -c
>../../../../../libstdc++-v3/src/c++17/floating_from_chars.cc -fPIC -DPIC
>-D_GLIBCXX_SHARED -o floating_from_chars.o
>../../../../../libstdc++-v3/src/c++17/floating_from_chars.cc: In function
>‘std::from_chars_result std::from_chars(const char*, const char*, _Float128&,
>chars_format)’:
>../../../../../libstdc++-v3/src/c++17/floating_from_chars.cc:1281:10: error:
>‘from_chars_strtod’ was not declared in this scope
> 1281 | return from_chars_strtod(first, last, value, fmt);
> | ^~~~~~~~~~~~~~~~~
>make[7]: *** [Makefile:587: floating_from_chars.lo] Error 1
/root cause analysis/
The symbol USE_STRTOD_FOR_FROM_CHARS is initially unknown. Since the target
system does not use locales, it will not be defined within the scope of
floating_to_chars.cc [1]:
>#if _GLIBCXX_HAVE_USELOCALE
>// FIXME: This should be reimplemented so it doesn't use strtod and newlocale.
>// That will avoid the need for any memory allocation, meaning that the
>// non-conforming errc::not_enough_memory result cannot happen.
># define USE_STRTOD_FOR_FROM_CHARS 1
>#endif
This results in code for from_chars_strtod() not being generated (lines 366 to
794) [2].
from_chars() implementation is generated either if USE_LIB_FAST_FLOAT or
USE_STRTOD_FOR_FROM_CHARS is enabled [3]. Within this section is code that
relies on USE_STRTOD_FOR_FROM_CHARS, but omits to check if the functionality is
available [4]
>#elif defined(USE_STRTOF128_FOR_FROM_CHARS)
>from_chars_result
>from_chars(const char* first, const char* last, _Float128& value,
> chars_format fmt) noexcept
>{
> // fast_float doesn't support IEEE binary128 format, but we can use strtold.
> return from_chars_strtod(first, last, value, fmt);
>}
>#endif
which results in the observed compilation error.
/proposed change/
Check if USE_STRTOD_FOR_FROM_CHARS is set before using from_chars_strtod():
--- a/libstdc++-v3/src/c++17/floating_from_chars.cc 2023-04-26
09:09:43.000000000 +0200
+++ b/libstdc++-v3/src/c++17/floating_from_chars.cc 2023-05-19
07:56:56.754330183 +0200
@@ -1264,6 +1264,8 @@
__attribute__((alias ("_ZSt10from_charsPKcS0_RdSt12chars_format")));
#endif
+#if defined(USE_STRTOD_FOR_FROM_CHARS)
+// otherwise there is no from_chars_strtod
#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
from_chars_result
from_chars(const char* first, const char* last, __ieee128& value,
@@ -1282,6 +1284,8 @@
}
#endif
+#endif // USE_STRTOD_FOR_FROM_CHARS
+
#endif // USE_LIB_FAST_FLOAT || USE_STRTOD_FOR_FROM_CHARS
_GLIBCXX_END_NAMESPACE_VERSION
[1]
https://github.com/gcc-mirror/gcc/blob/7f3df8e65c71e5df01fe7fe7de577bb9ff48f37b/libstdc%2B%2B-v3/src/c%2B%2B17/floating_from_chars.cc#L53-L58
[2]
https://github.com/gcc-mirror/gcc/blob/7f3df8e65c71e5df01fe7fe7de577bb9ff48f37b/libstdc%2B%2B-v3/src/c%2B%2B17/floating_from_chars.cc#L366-L794
[3]
https://github.com/gcc-mirror/gcc/blob/7f3df8e65c71e5df01fe7fe7de577bb9ff48f37b/libstdc%2B%2B-v3/src/c%2B%2B17/floating_from_chars.cc#L1230-L1342
[4]
https://github.com/gcc-mirror/gcc/blob/7f3df8e65c71e5df01fe7fe7de577bb9ff48f37b/libstdc%2B%2B-v3/src/c%2B%2B17/floating_from_chars.cc#L1317-L1340
