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Re: [RFC PATCH] configure: Poison (almost) all target-specific #defines


From: Thomas Huth
Subject: Re: [RFC PATCH] configure: Poison (almost) all target-specific #defines
Date: Tue, 16 Mar 2021 06:28:14 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0

On 15/03/2021 19.24, Eric Blake wrote:
On 3/15/21 8:54 AM, Thomas Huth wrote:
We are generating a lot of target-specific defines in the *-config-devices.h
and *-config-target.h files. Using them in common code is wrong and leads
to very subtle bugs since a "#ifdef CONFIG_SOMETHING" is not working there
as expected. To avoid these issues, we are already poisoning some of the
macros in include/exec/poison.h - but maintaining this list manually is
cumbersome. Thus let's generate the list of poisoned macros automatically
instead.
Note that CONFIG_TCG (which is also defined in config-host.h) and
CONFIG_USER_ONLY are special, so we have to filter these out.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
  RFC since the shell stuff in "configure" is quite ugly ... maybe there's
  a better way to do this via meson, but my meson-foo is still lacking...


+++ b/configure
@@ -6441,6 +6441,11 @@ if test -n "${deprecated_features}"; then
      echo "  features: ${deprecated_features}"
  fi
+cat *-config-devices.h *-config-target.h | grep '^#define ' \
+    | grep -v CONFIG_TCG | grep -v CONFIG_USER_ONLY \
+    | sed -e 's/#define //' -e 's/ .*//' | sort -u \
+    | sed -e 's/^/#pragma GCC poison /' > config-poison.h

Most times, a 'grep | sed' pipeline can be rewritten in pure sed.  In
this case:

cat *-config-devices.h *-config-target.h | \
   sed -n -e '/^#define / { s///; /CONFIG_TCG/d; /CONFIG_USER_ONLY/d;' \
          -e 's/ .*//; s/^/#pragma GCC poison /p; }' | \
   sort -u > config-poison.h

Thanks! I'll update my patch and use your suggestion (unless someone comes up with some Meson magic to do it there instead)

 Thomas





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