[Bug 778292]

[Alan Modra]

Not a gcc bug.

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https://bugs.launchpad.net/bugs/778292

Title:
  undefined reference to `pow' when building with -flto

Status in binutils:
  Fix Released
Status in The GNU Compiler Collection:
  Invalid
Status in “binutils” package in Ubuntu:
  In Progress
Status in “gcc-4.6” package in Ubuntu:
  Invalid
Status in “binutils” source package in Oneiric:
  In Progress
Status in “gcc-4.6” source package in Oneiric:
  Invalid

Bug description:
  Binary package hint: gcc-4.6

  cairo fails to build in oneiric, because linking with -flto results in
  an undefined reference:

  /bin/bash ../../libtool  --tag=CC   --mode=link gcc -D_REENTRANT   -I/usr/include/pixman-1        -I/usr/include/freetype2   -I/usr/include/libpng12             -Wall -Wextra -Wold-style-definition -Wdeclaration-after-statement -Wmissing-declarations -Werror-implicit-function-declaration -Wnested-externs -Wpointer-arith -Wwrite-strings -Wsign-compare -Wstrict-prototypes -Wmissing-prototypes -Wpacked -Wswitch-enum -Wmissing-format-attribute -Wbad-function-cast -Wvolatile-register-var -Wstrict-aliasing=2 -Winit-self -Wunsafe-loop-optimizations -Wno-missing-field-initializers -Wno-unused-parameter -Wno-attributes -Wno-long-long -Winline -Wlogical-op -fno-strict-aliasing -fno-common -flto -Wp,-D_FORTIFY_SOURCE=2 -DXCB_GENERIC_ERROR_HAS_MAJOR_MINOR_CODES                    -g -O2 -Wall -g -version-info 11002:2:11000 -no-undefined  -Wl,-Bsymbolic-functions -Wl,-z,defs -Wl,-O1 -Wl,--as-needed -o libcairo-script-interpreter.la -rpath /usr/lib/x86_64-linux-gnu libcairo_script_interpreter_la-cairo-script-file.lo libcairo_script_interpreter_la-cairo-script-hash.lo libcairo_script_interpreter_la-cairo-script-interpreter.lo libcairo_script_interpreter_la-cairo-script-objects.lo libcairo_script_interpreter_la-cairo-script-operators.lo libcairo_script_interpreter_la-cairo-script-scanner.lo libcairo_script_interpreter_la-cairo-script-stack.lo ../../src/libcairo.la -lpthread   -lpixman-1      -L/usr/lib/x86_64-linux-gnu -lfontconfig   -L/usr/lib/x86_64-linux-gnu -lfreetype   -L/usr/lib/x86_64-linux-gnu -lpng12   -L/usr/lib/x86_64-linux-gnu -lxcb-shm -lxcb   -L/usr/lib/x86_64-linux-gnu -lxcb-render -lxcb   -L/usr/lib/x86_64-linux-gnu -lXrender -lX11   -L/usr/lib/x86_64-linux-gnu -lX11             -lz -lz         -lz -lm
  libtool: link: gcc -shared  -fPIC -DPIC  .libs/libcairo_script_interpreter_la-cairo-script-file.o .libs/libcairo_script_interpreter_la-cairo-script-hash.o .libs/libcairo_script_interpreter_la-cairo-script-interpreter.o .libs/libcairo_script_interpreter_la-cairo-script-objects.o .libs/libcairo_script_interpreter_la-cairo-script-operators.o .libs/libcairo_script_interpreter_la-cairo-script-scanner.o .libs/libcairo_script_interpreter_la-cairo-script-stack.o   -Wl,-rpath -Wl,/build/buildd/cairo-1.10.2/debian/build/main/src/.libs -Wl,--as-needed ../../src/.libs/libcairo.so -lpthread -lpixman-1 -L/usr/lib/x86_64-linux-gnu -lfontconfig /usr/lib/x86_64-linux-gnu/libfreetype.so -lpng12 -lxcb-shm -lxcb-render -lxcb -lXrender -lX11 -lz -lm  -flto -O2 -Wl,-Bsymbolic-functions -Wl,-z -Wl,defs -Wl,-O1   -Wl,-soname -Wl,libcairo-script-interpreter.so.2 -o .libs/libcairo-script-interpreter.so.2.11000.2
  /tmp/ccbzCZUW.ltrans11.ltrans.o: In function `_csi_parse_number':
  ccbzCZUW.ltrans11.o:(.text+0x1074): undefined reference to `pow'
  collect2: ld returned 1 exit status
  /tmp/ccJCGA7g.ltrans11.ltrans.o: In function `_csi_parse_number':
  ccJCGA7g.ltrans11.o:(.text+0x1074): undefined reference to `pow'
  collect2: ld returned 1 exit status

  https://launchpad.net/ubuntu/+source/cairo/1.10.2-2ubuntu3/+buildjob/2530315

  Given that -lm is being explicitly passed, and pow is a symbol
  provided by libm, that looks like a bug in gcc to me?

  Running the same command without -flto works just fine.

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