On 04/09/2018 11:21 AM, Yaakov Selkowitz wrote:
On 2018-04-09 03:59, Florian Weimer wrote:
Is there a recommend way to get libtool to pass through all flags
specified in CFLAGS and LDFLAGS unchanged, and have the GCC compiler
driver sort out which flags to pass to the compiler/assembler/linker?
$ libtool --mode=compile --help
[snip]
This mode accepts the following additional options:
[snip]
-Wc,FLAG pass FLAG directly to the compiler
$ libtool --mode=link --help
[snip]
The following components of LINK-COMMAND are treated specially:
[snip]
-Wc,FLAG
-Xcompiler FLAG pass linker-specific FLAG directly to the compiler
-Wl,FLAG
-Xlinker FLAG pass linker-specific FLAG directly to the linker
That doesn't solve the problem because there is a difference between
passing a flag to the *linker* and passing it to the *compiler driver*
while linking.
For LTO support, we should pass *all* of CFLAGS again during the linker
compiler driver invocation. And libtool shouldn't try to guess which
flags are needed in which phase.
Honestly, I have no idea why libtool tries to reimplement the compiler
driver on GNU. I can see that it's needed on some other systems. If
something doesn't work with GCC, we need to fix GCC, and not rewrite
flags in libtool in undocumented ways.
But, often when this happens, it is the fault of a poorly written
configure.ac or Makefile.am. Where exactly are you seeing an issue?
Everywhere? libtool does not pass -specs= arguments in LDFLAGS to the
linker invocation.
Thanks,
Florian
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