Gather and clean up compiler flags

[kliem]

We gather and clean up compiler flags. Also we

• add --enable-fat-binary to configure (as an alternative to setting SAGE_FAT_BINARY)
• add --enable_debug={no|symbols|yes} as alternative to setting SAGE_DEBUG
• compile with -Og -g if SAGE_DEBUG=yes
• compile with -O2 if SAGE_DEBUG=no (some packages with O3 instead)
• compile with -O2 -g otherwise (some packages with O3 instead)

During the build of Sage there are now flags that can be exported
in spkg_install.in with one line, instead of checking SAGE_DEBUG
etc. for each individual package, e.g. by

• export CFLAGS=$CFLAGS (redundant, use flags as above)
• export CFLAGS=$CFLAGS_O3 (O3 instead of O2, but only if not in debug mode)
• export CFLAGS=$ORIGINAL_CFLAGS (use $CFLAGS as set before configure)

Likewise we do with CXXFLAGS, FCFLAGS, F77FLAGS.

We try to respect the user's choice and do not overwrite the flags if already
set by the user, but only add compile flags if necessary for packages to work.

Inidividual packages can still be compiled with specified flags or in debug mode using

make CFLAGS=-O2 some-package

or

make SAGE_DEBUG="yes" some-package

This ticket prepares #27122, which adds -march=native to the defaults.

CC: @slel @dimpase

Component: build

Keywords: compile flags, sd111

Author: Jonathan Kliem

Branch/Commit: 3bb3099

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/30375

[slel]

Description changed:

--- 
+++ 
@@ -1,28 +1,33 @@
 We gather and clean up compiler flags. Also we
 
-    add --enable-fat-binary to configure (as an alternative to setting SAGE_FAT_BINARY)
-    add --enable_debug={no|symbols|yes} as alternative to setting SAGE_DEBUG 
+- add `--enable-fat-binary` to `configure` (as an alternative to setting `SAGE_FAT_BINARY`)
+- add `--enable_debug={no|symbols|yes}` as alternative to setting `SAGE_DEBUG`
+- compile with `-Og -g` if `SAGE_DEBUG=yes`
+- compile with `-O2` if `SAGE_DEBUG=no` (some packages with `O3` instead)
+- compile with `-O2 -g` otherwise (some packages with `O3` instead)
 
-    compile with -Og -g if SAGE_DEBUG=yes
-    compile with -O2 if SAGE_DEBUG=no (some packages with O3 instead)
-    compile with -O2 -g otherwise (some packages with O3 instead) 
+During the build of Sage there are now flags that can be exported
+in `spkg_install.in` with one line, instead of checking `SAGE_DEBUG`
+etc. for each individual package, e.g. by
 
-During the build of sage there are now flags that can be exported in spkg_install.in with one line, instead of checking SAGE_DEBUG etc. for each individual package, e.g. by
+- `export CFLAGS=$CFLAGS` (redundant, use flags as above)
+- `export CFLAGS=$CFLAGS_O3` (`O3` instead of `O2`, but only if not in debug mode)
+- `export CFLAGS=$ORIGINAL_CFLAGS` (use `$CFLAGS` as set before `configure`)
 
-    export CFLAGS=$CFLAGS (redundant, use flags as above)
-    export CFLAGS=$CFLAGS_O3 (O3 instead of O2, but only if not in debug mode)
-    export CFLAGS=$ORIGINAL_CFLAGS (use $CFLAGS as set before configure) 
+Likewise we do with `CXXFLAGS`, `FCFLAGS`, `F77FLAGS`.
 
-Likewise we do with CXXFLAGS, FCFLAGS, F77FLAGS.
-
-We try to respect the users choice and do not overwrite the flags if already set by the user, but only add compile flags if necessary for packages to work.
+We try to respect the user's choice and do not overwrite the flags if already
+set by the user, but only add compile flags if necessary for packages to work.
 
 Inidividual packages can still be compiled with specified flags or in debug mode using
 
+```
 make CFLAGS=-O2 some-package
-
+```
 or
 
+```
 make SAGE_DEBUG="yes" some-package
+```
+This ticket prepares #27122, which adds `-march=native` to the defaults.
 
-This ticket prepares #27122, which adds `-march=native` to the defaults.

[mkoeppe]

comment:3

One point that probably needs discussion is the following.

When an spkg is built, the current design of sage-spkg is to create a self-contained script spkg-install that sets all necessary environment variables (by sourcing sage-env etc.). (This makes it relatively easy to debug the installation process.)

Making package installs depend on exported environment variables in Makefile.in breaks this design.

It would probably be better to create a new script sage-build-env (to complement sage-build-env-config) to take care of these environment variable settings.

[kliem]

comment:4

Ok, I think I'm beginning to understand.

Create a new file build/bin/sage-build-env.in and move the stuff that I added to the makefile there?

Then make sure build/bin/sage-build-env is added to the correct places?

Why should I not add the things to build/bin/sage-build-env-config directly?

[mkoeppe]

comment:5

Replying to @kliem:

Create a new file build/bin/sage-build-env.in and move the stuff that I added to the makefile there?

Then make sure build/bin/sage-build-env is added to the correct places?

Yes

Why should I not add the things to build/bin/sage-build-env-config directly?

Just a suggestion, to keep the analogy to src/bin/sage-env (which implements some logic) and src/bin/sage-env-config (which purely sets some variables). Not very important.

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

b6cf7c1

Merge branch 'u/gh-kliem/gather_and_clean_up_compile_flags' of git://trac.sagemath.org/sage into u/gh-kliem/gather_and_clean_up_compile_flags_new

[sagetrac-git]

Changed commit from 2ff5630 to b6cf7c1

[sagetrac-git]

Changed commit from b6cf7c1 to 5f4d0b1

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

5f4d0b1

bash syntax again