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<p>When I build glibc in two different places, I get
non-reproducible results - a 4-byte difference:</p>
<blockquote>
<p><tt>$ cmp -l
~/workspace/upstream[12]/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/package/lib/libc-2.28.so</tt><tt><br>
</tt><tt>1259181 71 172</tt><tt><br>
</tt><tt>1259182 27 304</tt><tt><br>
</tt><tt>1259183 152 77</tt><tt><br>
</tt><tt>1259184 363 243</tt></p>
</blockquote>
<p>These 4 bytes are the checksum that objcopy --add-gnu-debuglink
adds to the binary when the .debug info is split out at do_package
time, see package.bbclass +416</p>
<p>So why is the debug info different? We add -fdebug-prefix-map to
our CFLAGS, which ensures that all our intra-component debug paths
are prefixed with /usr/src/debug/glibc/, for instance, but this
isn't working in this case. The difference is happening in
csu/crt1.o, which is being linked into libc.so (and others):</p>
<blockquote>
<p><tt>$
../recipe-sysroot-native/usr/bin/arm-tait-linux-gnueabi/arm-tait-linux-gnueabi-objdump
-t csu/crt1.o</tt><tt><br>
</tt><tt>...</tt><tt><br>
</tt><tt>00000000 l df *ABS* 00000000
/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/build-arm-tait-linux-gnueabi/csu/abi-note.o</tt><tt><br>
</tt><tt>00000000 l df *ABS* 00000000
/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/build-arm-tait-linux-gnueabi/csu/start.o</tt><br>
</p>
</blockquote>
This abi-note.o symbol is finding its way into libc.so:
<blockquote>
<p><tt>$
../recipe-sysroot-native/usr/bin/arm-tait-linux-gnueabi/arm-tait-linux-gnueabi-objdump
-t libc.so<br>
...</tt><tt><br>
</tt><tt>00000000 l df *ABS* 00000000
/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/build-arm-tait-linux-gnueabi/csu/abi-note.o</tt></p>
</blockquote>
So where does csu/crt1.o come from?<br>
<blockquote>
<blockquote> </blockquote>
<p><tt>$ arm-tait-linux-gnueabi-gcc -march=armv5te -marm
-mcpu=arm926ej-s
--sysroot=/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/recipe-sysroot
-nostdlib -nostartfiles </tt><tt><b>-r -o
/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/build-arm-tait-linux-gnueabi/csu/crt1.o</b></tt><tt>
/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/build-arm-tait-linux-gnueabi/csu/start.o
/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/build-arm-tait-linux-gnueabi/csu/abi-note.o
/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/build-arm-tait-linux-gnueabi/csu/init.o
/home/douglas/workspace/upstream1/build/tmp/work/armv5e-tait-linux-gnueabi/glibc/2.28-r0/build-arm-tait-linux-gnueabi/csu/static-reloc.o</tt></p>
<blockquote> </blockquote>
</blockquote>
<p>Note the -r = --relocatable, an ld option, which, "Generate[s]
relocatable output---i.e., generate[s] an output file that can in
turn serve as input to ld. This is often called partial linking",
ie. the glibc build is just putting these .o files together for
later convenience.</p>
<p>Regrettably, this command both ignores -fdebug-prefix-map (which
ld doesn't accept) and puts the fully-qualified path to some of
the input .o files in the resulting crt1.o. At package
splitdebuginfo() time, although the fully-qualified path info is
split off into the .debug files, a (relative) path to the .debug
files plus a checksum is tacked onto libc.so by objcopy
--add-gnu-debuglink ... and the checksum depends on the path to
the build.</p>
<p>There is a work-around: turn off the debug packaging:</p>
<blockquote>
<p><tt>INHIBIT_PACKAGE_DEBUG_SPLIT_pn-glibc = "1"</tt><br>
</p>
</blockquote>
<p>I don't have a solution for this. Suggestions?</p>
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