Re: [PATCH] Use meson's detected python installation

[Paolo Bonzini]

On 9/4/25 17:11, Peter Foley wrote:
Relying on `python3` to be avilable in $PATH doesn't work in some build
environments. Update the build files to use the found python binary
explicitly.

Meson already does this, if the file is not executable.  See 
docs/devel/build-system.rst:

  Meson has a special convention for invoking Python scripts: if their
  first line is ``#! /usr/bin/env python3`` and the file is *not*
  executable, find_program() arranges to invoke the script under the
  same Python interpreter that was used to invoke Meson.  This is the
  most common and preferred way to invoke support scripts from Meson
  build files, because it automatically uses the value of configure's
  --python= option.

Using "[python, 'foo']" is only needed for scripts "where it is 
desirable to make the script executable (for example for test scripts 
that developers may want to invoke from the command line, such as 
tests/qapi-schema/test-qapi.py)".

I think the only file you touched that is executable is 
scripts/qemu-plugin-symbols.py; so your issue can be fixed without code 
changes, and with a patch that only does "chmod -x 
scripts/qemu-plugin-symbols.py".  Please correct me if I'm wrong though!

Thanks,

Paolo

Signed-off-by: Peter Foley <pefo...@google.com>
---
  block/meson.build   |  6 ++----
  meson.build         | 10 +++++-----
  plugins/meson.build |  2 +-
  3 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/block/meson.build b/block/meson.build
index 
34b1b2a30630214959630d5543181bc82a54d2b3..67e9bee1210307ff15ca87ba0f5e7f785df15042
 100644
--- a/block/meson.build
+++ b/block/meson.build
@@ -139,14 +139,12 @@ if get_option('dmg').allowed()
    endforeach
  endif
  
-module_block_py = find_program('../scripts/modules/module_block.py')
  module_block_h = custom_target('module_block.h',
                                 output: 'module_block.h',
                                 input: modsrc,
-                               command: [module_block_py, '@OUTPUT0@', modsrc])
+                               command: [python, 
files('../scripts/modules/module_block.py'), '@OUTPUT0@', modsrc])
  block_ss.add(module_block_h)
  
-wrapper_py = find_program('../scripts/block-coroutine-wrapper.py')
  block_gen_c = custom_target('block-gen.c',
                              output: 'block-gen.c',
                              input: files(
@@ -158,7 +156,7 @@ block_gen_c = custom_target('block-gen.c',
                                        '../include/system/block-backend-io.h',
                                        'coroutines.h'
                                        ),
-                            command: [wrapper_py, '@OUTPUT@', '@INPUT@'])
+                            command: [python, 
files('../scripts/block-coroutine-wrapper.py'), '@OUTPUT@', '@INPUT@'])
  block_ss.add(block_gen_c)
  
  block_ss.add(files('stream.c'))
diff --git a/meson.build b/meson.build
index 
fa6186db33435c26d06dce2971a9f536250607e0..6e8baf3deb13c172eecd371ea302b1c2539048d0
 100644
--- a/meson.build
+++ b/meson.build
@@ -12,8 +12,6 @@ add_test_setup('slow', exclude_suites: ['thorough'],
  add_test_setup('thorough',
                 env: ['G_TEST_SLOW=1', 'SPEED=thorough', 'RUST_BACKTRACE=1'])
  
-meson.add_postconf_script(find_program('scripts/symlink-install-tree.py'))
-
  ####################
  # Global variables #
  ####################
@@ -76,6 +74,8 @@ have_user = have_linux_user or have_bsd_user
  sh = find_program('sh')
  python = import('python').find_installation()
  
+meson.add_postconf_script([python, 'scripts/symlink-install-tree.py'])
+
  cc = meson.get_compiler('c')
  all_languages = ['c']
  if host_os == 'windows' and add_languages('cpp', required: false, native: 
false)
@@ -3474,7 +3474,7 @@ foreach target : target_dirs
        output: config_devices_mak,
        depfile: config_devices_mak + '.d',
        capture: true,
-      command: [minikconf,
+      command: [python, minikconf,
                  get_option('default_devices') ? '--defconfig' : 
'--allnoconfig',
                  config_devices_mak, '@DEPFILE@', '@INPUT@',
                  host_kconfig, target_kconfig])
@@ -3545,8 +3545,8 @@ config_host_h = configure_file(output: 'config-host.h', 
configuration: config_ho
  genh += config_host_h
  
  hxtool = find_program('scripts/hxtool')
-shaderinclude = find_program('scripts/shaderinclude.py')
-qapi_gen = find_program('scripts/qapi-gen.py')
+shaderinclude = [python, 'scripts/shaderinclude.py']
+qapi_gen = [python, 'scripts/qapi-gen.py']
  qapi_gen_depends = [ meson.current_source_dir() / 'scripts/qapi/__init__.py',
                       meson.current_source_dir() / 'scripts/qapi/commands.py',
                       meson.current_source_dir() / 'scripts/qapi/common.py',
diff --git a/plugins/meson.build b/plugins/meson.build
index 
62c991d87fcdd8bcde8edddcc73909c6133f5460..6bf72a69060414ba1b7c1857515eeceb5a2c7b7c
 100644
--- a/plugins/meson.build
+++ b/plugins/meson.build
@@ -6,7 +6,7 @@ qemu_plugin_symbols = configure_file(
    input: files('../include/qemu/qemu-plugin.h'),
    output: 'qemu-plugin.symbols',
    capture: true,
-  command: [files('../scripts/qemu-plugin-symbols.py'), '@INPUT@'])
+  command: [python, files('../scripts/qemu-plugin-symbols.py'), '@INPUT@'])
  
  # Modules need more symbols than just those in plugins/qemu-plugins.symbols
  if not enable_modules

---
base-commit: baa79455fa92984ff0f4b9ae94bed66823177a27
change-id: 20250904-python-78ccebd0fded

Best regards,