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buildflags.md: Move toolchain selection documentation from macros file

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This commit is contained in:
Florian Weimer 2021-11-15 15:34:15 +01:00
parent ac57cc99aa
commit a9123ea1ac
2 changed files with 27 additions and 23 deletions
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27
buildflags.md
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@ -75,6 +75,33 @@ It is possible to set RPM macros to change some aspects of the
compiler flags. Changing these flags should be used as a last compiler flags. Changing these flags should be used as a last
recourse if other workarounds are not available. recourse if other workarounds are not available.
### Toolchain selection
The default toolchain uses GCC, and the `%toolchain` macro is defined
as `gcc`.
It is enough to override `toolchain` macro and all relevant macro for C/C++
compilers will be switched. Either in the spec or in the command-line.
%global toolchain clang
or:
rpmbuild -D "toolchain clang" …
Inside a spec file it is also possible to determine which toolchain is in use
by testing the same macro. For example:
%if "%{toolchain}" == "gcc"
BuildRequires: gcc
%endif
or:
%if "%{toolchain}" == "clang"
BuildRequires: clang compiler-rt
%endif
### Lazy binding ### Lazy binding
If your package depends on the semantics of lazy binding (e.g., it has If your package depends on the semantics of lazy binding (e.g., it has

23
macros
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@ -37,29 +37,6 @@
%__cpp_clang clang-cpp %__cpp_clang clang-cpp
# Default to the GCC toolchain # Default to the GCC toolchain
#
# It is enough to override `toolchain` macro and all relevant macro for C/C++
# compilers will be switched. Either in the spec or in the command-line.
#
# %global toolchain clang
#
# or:
#
# rpmbuild -D "toolchain clang" …
#
# Inside a spec file it is also possible to determine which toolchain is in use
# by testing the same macro. For example:
#
# %if "%{toolchain}" == "gcc"
# BuildRequires: gcc
# %endif
#
# or:
#
# %if "%{toolchain}" == "clang"
# BuildRequires: clang compiler-rt
# %endif
#
%toolchain gcc %toolchain gcc
%__cc %{expand:%%{__cc_%{toolchain}}} %__cc %{expand:%%{__cc_%{toolchain}}}