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Posted to commits@nuttx.apache.org by GitBox <gi...@apache.org> on 2022/04/28 09:21:05 UTC
[GitHub] [incubator-nuttx-apps] pussuw opened a new pull request, #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
pussuw opened a new pull request, #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157
lxx must be before lmm at least, because new uses malloc().
## Summary
Fixes C++ library linkage with CONFIG_BUILD_KERNEL
## Impact
## Testing
icicle:knsh
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[GitHub] [incubator-nuttx-apps] pkarashchenko merged pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pkarashchenko merged PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157
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[GitHub] [incubator-nuttx-apps] pussuw commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pussuw commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1111976522
> What is the exact error with the current code? I mean do we use start/end group for the libs? Otherwise I do not see why order should matter here
libcxx refers to e.g. malloc which is in libmm, the ordering matters here, otherwise e.g. malloc will be left undefined in applications that use libxx but don't use malloc directly.
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[GitHub] [incubator-nuttx-apps] pussuw commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pussuw commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112945999
> I think you are hitting this issue [apache/incubator-nuttx#6082](https://github.com/apache/incubator-nuttx/issues/6082)
That issue is different I think, it is on the export side. What I face is that when linking e.g. cxxtest app, the resulting elf file has undefined symbols after ELFLD. Please keep in mind that this is with CONFIG_BUILD_KERNEL, every application is build separately into one .elf file which can be started e.g. via posix_spawn(), so this is quite different from the monolithic build process used by BUILD_FLAT and even BUILD_PROTECTED.
```
/apps/bin_copy$ objdump -t cxxtest_stripped | grep UND
0000000000000000 *UND* 0000000000000000 malloc
0000000000000000 *UND* 0000000000000000 on_exit
0000000000000000 *UND* 0000000000000000 syslog
0000000000000000 *UND* 0000000000000000 free
```
The problem I think is ELFLD does not have the start/end group encapsulation, like the kernel side does:
`$(LDSTARTGROUP) $(LDLIBS) $(EXTRA_LIBS) $(LDENDGROUP)`
```
define ELFLD
@echo "LD: $2"
$(Q) $(LD) $(LDELFFLAGS) $(LDLIBPATH) $(ARCHCRT0OBJ) $1 $(LDLIBS) -o $2
endef
```
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[GitHub] [incubator-nuttx-apps] gustavonihei commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
gustavonihei commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112572090
> There is no cli error, the error comes from the elf loader because it encounters an undefined symbol it cannot resolve / relocate. I'll provide a more detailed error description tomorrow, but the short description is referencing symbols from libxx to e.g. symbols in libmm. The kernel mode ldlibs flag does not show start/end group. LDELF is called and there is no encapsulation either. All I know that appending lxx results in undefined symbols in the resulting cxx application elf.
>
> Maybe the fix is to add usage of start/end group to kernel mode ldflags
https://github.com/apache/incubator-nuttx-apps/blob/a5a4c561fb9c9c5c9af0013f2c3b8901a176b956/Application.mk#L133-L136
If adding wrapping `LDLIBS` with `LDSTARTGROUP` and `LDENDGROUP` works, I believe this would be the definitive fix for the issue.
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[GitHub] [incubator-nuttx-apps] pussuw commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pussuw commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112580192
>
> If wrapping `LDLIBS` with `LDSTARTGROUP` and `LDENDGROUP` works, I believe this would be the definitive fix for the issue.
Agreed, I'll try that tomorrow
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[GitHub] [incubator-nuttx-apps] gustavonihei commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
gustavonihei commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112549893
I agree with @pkarashchenko. NuttX usually wraps the libraries around `--start-group` and `--end-group` (via `LDSTARTGROUP` and `LDENDGROUP`), so the ordering of libraries should not matter because those libraries within the group will be searched repeatedly until all symbols are found.
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[GitHub] [incubator-nuttx-apps] pkarashchenko commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pkarashchenko commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112552721
@pussuw maybe you can share the command line call that generates an error so we can take a look at the arguments that are passed during the link stage?
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[GitHub] [incubator-nuttx-apps] pussuw commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pussuw commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112565673
There is no cli error, the error comes from the elf loader because it encounters an undefined symbol it cannot resolve / relocate. I'll provide a more detailed error description tomorrow, but the short description is references to symbols in libxx to e.g. symbols in libmm. The kernel mode ldlibs flag does not show start/end group. LDELF is called and there is no encapsulation either. All I know that appending lxx results in undefined symbols in the resulting cxx application elf.
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[GitHub] [incubator-nuttx-apps] pkarashchenko commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pkarashchenko commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112948666
> $(LDSTARTGROUP) $(LDLIBS) $(LDENDGROUP) fixes the issue, thanks for the help guys
Great!
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[GitHub] [incubator-nuttx-apps] pussuw commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pussuw commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112948371
$(LDSTARTGROUP) $(LDLIBS) $(LDENDGROUP) fixes the issue, thanks for the help guys
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[GitHub] [incubator-nuttx-apps] pkarashchenko commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pkarashchenko commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1112918403
I think you are hitting this issue https://github.com/apache/incubator-nuttx/issues/6082
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[GitHub] [incubator-nuttx-apps] pkarashchenko commented on pull request #1157: import/Make.defs: Fix C++ library linkage with CONFIG_BUILD_KERNEL
Posted by GitBox <gi...@apache.org>.
pkarashchenko commented on PR #1157:
URL: https://github.com/apache/incubator-nuttx-apps/pull/1157#issuecomment-1111969837
What is the exact error with the current code?
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