FLAG-O-MATIC.ECLASS

Section: eclass-manpages (5)
Updated: Oct 2025
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NAME

flag-o-matic.eclass - common functions to manipulate and query toolchain flags

DESCRIPTION

This eclass contains a suite of functions to help developers sanely and safely manage toolchain flags in their builds.

SUPPORTED EAPIS

7 8

FUNCTIONS

all-flag-vars

Return all the flag variables that our high level functions operate on.

filter-flags <flags>

Remove particular <flags> from {C,CPP,CXX,CCAS,F,FC,LD}FLAGS. Accepts shell globs.

filter-lfs-flags

Remove flags that enable Large File Support.

filter-lto

Remove flags that enable LTO and those that depend on it

filter-ldflags <flags>

Remove particular <flags> from LDFLAGS. Accepts shell globs.

append-cppflags <flags>

Add extra <flags> to the current CPPFLAGS.

append-cflags <flags>

Add extra <flags> to the current CFLAGS. If a flag might not be supported with different compilers (or versions), then use test-flags-CC like so:

append-cflags $(test-flags-CC -funky-flag)

append-cxxflags <flags>

Add extra <flags> to the current CXXFLAGS. If a flag might not be supported with different compilers (or versions), then use test-flags-CXX like so:

append-cxxflags $(test-flags-CXX -funky-flag)

append-fflags <flags>

Add extra <flags> to the current {F,FC}FLAGS. If a flag might not be supported with different compilers (or versions), then use test-flags-F77 like so:

append-fflags $(test-flags-F77 -funky-flag)

append-lfs-flags

Add flags that enable Large File Support.

append-ldflags <flags>

Add extra <flags> to the current LDFLAGS.

append-flags <flags>

Add extra <flags> to your current {C,CXX,F,FC}FLAGS.

replace-flags <old> <new>

Replace the <old> flag with <new>. Accepts shell globs for <old>.

replace-cpu-flags <old> <new>

Replace cpu flags (like -march/-mcpu/-mtune) that select the <old> cpu with flags that select the <new> cpu. Accepts shell globs for <old>.

is-flagq <flag>

Returns shell true if <flag> is in {C,CXX,F,FC}FLAGS, else returns shell false. Accepts shell globs.

is-flag <flag>

Echo's "true" if flag is set in {C,CXX,F,FC}FLAGS. Accepts shell globs.

is-ldflagq <flag>

Returns shell true if <flag> is in LDFLAGS, else returns shell false. Accepts shell globs.

is-ldflag <flag>

Echo's "true" if flag is set in LDFLAGS. Accepts shell globs.

filter-mfpmath <math types>

Remove specified math types from the fpmath flag. For example, if the user has -mfpmath=sse,386, running `filter-mfpmath sse` will leave the user with -mfpmath=386.

strip-flags

Strip *FLAGS of everything except known good/safe flags. This runs over all flags returned by all_flag_vars().

test-flag-CC <flag>

Returns shell true if <flag> is supported by the C compiler, else returns shell false.

test-flag-CXX <flag>

Returns shell true if <flag> is supported by the C++ compiler, else returns shell false.

test-flag-F77 <flag>

Returns shell true if <flag> is supported by the Fortran 77 compiler, else returns shell false.

test-flag-FC <flag>

Returns shell true if <flag> is supported by the Fortran 90 compiler, else returns shell false.

test-flag-CCLD <flag>

Returns shell true if <flag> is supported by the C compiler and linker, else returns shell false.

test-flag-HIPCXX <flag>

Returns shell true if <flag> is supported by the HIP compiler, else returns shell false.

test-flags-CC <flags>

Returns shell true if <flags> are supported by the C compiler, else returns shell false.

test-flags-CXX <flags>

Returns shell true if <flags> are supported by the C++ compiler, else returns shell false.

test-flags-F77 <flags>

Returns shell true if <flags> are supported by the Fortran 77 compiler, else returns shell false.

test-flags-FC <flags>

Returns shell true if <flags> are supported by the Fortran 90 compiler, else returns shell false.

test-flags-CCLD <flags>

Returns shell true if <flags> are supported by the C compiler and default linker, else returns shell false.

test-flags-HIPCXX <flags>

Returns shell true if <flags> are supported by the HIP compiler and default linker, else returns shell false.

test-flags <flags>

Short-hand that should hopefully work for both C and C++ compiler, but its really only present due to the append-flags() abomination.

test_version_info <version>

Returns shell true if the current C compiler version matches <version>, else returns shell false. Accepts shell globs.

strip-unsupported-flags

Strip {C,CXX,F,FC,HIP}FLAGS of any flags not supported by the active toolchain.

get-flag <flag>

Find and echo the value for a particular flag. Accepts shell globs.

replace-sparc64-flags

Sets mcpu to v8 and uses the original value as mtune if none specified.

append-libs <libs>

Add extra <libs> to the current LIBS. All arguments should be prefixed with either -l or -L. For compatibility, if arguments are not prefixed as options, they are given a -l prefix automatically.

raw-ldflags [flags]

Turn C style ldflags (-Wl,-foo) into straight ldflags - the results are suitable for passing directly to 'ld'; note LDFLAGS is usually passed to gcc where it needs the '-Wl,'.

If no flags are specified, then default to ${LDFLAGS}.

no-as-needed

Return value: Flag to disable asneeded behavior for use with append-ldflags.

test-compile <language> <code>

Attempts to compile (and possibly link) the given program. The first <language> parameter corresponds to the standard -x compiler argument. If the program should additionally be attempted to be linked, the string "+ld" should be added to the <language> parameter.

append-atomic-flags

Attempts to detect if appending -latomic works, and does so.

MAINTAINERS

[email protected]

REPORTING BUGS

Please report bugs via https://bugs.gentoo.org/

FILES

flag-o-matic.eclass

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Time: 03:27:00 GMT, October 25, 2025