toolchain/crosstool-NG: disable decimal floats

Decimal floats were introduced circa gcc-4.2 or -4.3, and requires the floating-point environement fenv.h in the C library.

The uClibc .config file used by crosstool-NG to build uClibc is the same as used by the internal buildroot mechanism, and explcitly disables fenv support.

The quick workaround is to simply disable decimal floats in all crosstool-NG config files.

In the long run, it might be better to check this situation, and/or add code and/or options in crosstool-NG to handle this (but it is much more involved, and this workaround is sane).

---
 .../crosstool-ng.config-eglibc                     |    4 ++--
 .../crosstool-ng.config-glibc                      |    4 ++--
 .../crosstool-ng.config-uClibc                     |    4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

index c1ab679..4488d02 100644
@@ -273,8 +273,8 @@ CT_CC_LANG_CXX=y
 # gcc other options
 #
 CT_CC_ENABLE_CXX_FLAGS=""
-CT_CC_CORE_EXTRA_CONFIG_ARRAY=""
-CT_CC_EXTRA_CONFIG_ARRAY=""
+CT_CC_CORE_EXTRA_CONFIG_ARRAY="--disable-decimal-float"
+CT_CC_EXTRA_CONFIG_ARRAY="--disable-decimal-float"
 CT_CC_STATIC_LIBSTDCXX=y
 
 #

index 4a555c7..46a636b 100644
@@ -273,8 +273,8 @@ CT_CC_LANG_CXX=y
 # gcc other options
 #
 CT_CC_ENABLE_CXX_FLAGS=""
-CT_CC_CORE_EXTRA_CONFIG_ARRAY=""
-CT_CC_EXTRA_CONFIG_ARRAY=""
+CT_CC_CORE_EXTRA_CONFIG_ARRAY="--disable-decimal-float"
+CT_CC_EXTRA_CONFIG_ARRAY="--disable-decimal-float"
 CT_CC_STATIC_LIBSTDCXX=y
 
 #

index 0e442f0..437f455 100644
@@ -272,8 +272,8 @@ CT_CC_LANG_CXX=y
 # gcc other options
 #
 CT_CC_ENABLE_CXX_FLAGS=""
-CT_CC_CORE_EXTRA_CONFIG_ARRAY=""
-CT_CC_EXTRA_CONFIG_ARRAY=""
+CT_CC_CORE_EXTRA_CONFIG_ARRAY="--disable-decimal-float"
+CT_CC_EXTRA_CONFIG_ARRAY="--disable-decimal-float"
 CT_CC_STATIC_LIBSTDCXX=y
 
 #

1.7.2.5

Wouldn't it be better to enable FENV in buildroot's uClibc config?

I remember there were some packages that had problems with it too.

Regards,
Arnout

Arnout Vandecappelle                               arnout at mind be
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Arnout> Wouldn't it be better to enable FENV in buildroot's uClibc config?

It's afaik only available for i386, and even then I believe some things are missing.

Bye, Peter Korsgaard

I did not want to impact the internal backend, thus the workaround is limited to the crosstool-NG backend. This limits the impact for the now-woon-to-be-released next version of BR.

Switching to enabling fenv by default can be done in the next cycle.

khem told me yesterday on IRC that uClibc had a working fenv for all supported architectures, with no _known_ problems (which does not mean there is none, just that none is known so far):
http://ibot.rikers.org/%23uclibc/20120515.html.gz @ 20:20:25 - 20:56.17

Regards,
Yann E. MORIN.

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| +0/33 662376056 | Software  Designer | \ / CAMPAIGN     |   ^                |
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Arnout> Wouldn't it be better to enable FENV in buildroot's uClibc config?

Yann> I did not want to impact the internal backend, thus the workaround is Yann> limited to the crosstool-NG backend. This limits the impact for the Yann> now-woon-to-be-released next version of BR.

Yann> Switching to enabling fenv by default can be done in the next cycle.

Agreed, lets keep it simple for now.

Yann> khem told me yesterday on IRC that uClibc had a working fenv for all Yann> supported architectures, with no _known_ problems (which does not mean Yann> there is none, just that none is known so far):
Yann> http://ibot.rikers.org/%23uclibc/20120515.html.gz @ 20:20:25 - 20:56.17

Yes, I saw that as well, but looking at the uClibc sources I only see .c files for i386 and sh4.

Bye, Peter Korsgaard

Yann> Decimal floats were introduced circa gcc-4.2 or -4.3, and requires Yann> the floating-point environement fenv.h in the C library.

Yann> The uClibc .config file used by crosstool-NG to build uClibc is the Yann> same as used by the internal buildroot mechanism, and explcitly Yann> disables fenv support.

Yann> The quick workaround is to simply disable decimal floats in all Yann> crosstool-NG config files.

Yann> In the long run, it might be better to check this situation, and/or Yann> add code and/or options in crosstool-NG to handle this (but it is Yann> much more involved, and this workaround is sane).

Committed, thanks.

Bye, Peter Korsgaard