compilers: Try harder to dedup builtin libs

-ldl, -lm, -lpthread should always be de-duplicated, no matter what.

Closes #2150

mesonbuild/compilers/compilers.py

@@ -659,6 +659,9 @@ class CompilerArgs(list):
     # Only UNIX shared libraries require this. Others have a fixed extension.
     dedup1_regex = re.compile(r'([\/\\]|\A)lib.*\.so(\.[0-9]+)?(\.[0-9]+)?(\.[0-9]+)?$')
     dedup1_args = ('-c', '-S', '-E', '-pipe', '-pthread')
+    # In generate_link() we add external libs without de-dup, but we must
+    # *always* de-dup these because they're special arguments to the linker
+    always_dedup_args = ('-ldl', '-lm', '-lpthread')
     compiler = None
 
     def _check_args(self, args):
@@ -793,7 +796,7 @@ def extend_preserving_lflags(self, iterable):
         normal_flags = []
         lflags = []
         for i in iterable:
-            if i.startswith('-l') or i.startswith('-L'):
+            if i not in self.always_dedup_args and (i.startswith('-l') or i.startswith('-L')):
                 lflags.append(i)
             else:
                 normal_flags.append(i)

run_unittests.py

@@ -5039,6 +5039,19 @@ def test_ldflag_dedup(self):
                 max_count = max(max_count, line.count(search_term))
         self.assertEqual(max_count, 1, 'Export dynamic incorrectly deduplicated.')
 
+    def test_compiler_libs_static_dedup(self):
+        testdir = os.path.join(self.unit_test_dir, '55 dedup compiler libs')
+        self.init(testdir)
+        build_ninja = os.path.join(self.builddir, 'build.ninja')
+        with open(build_ninja, 'r', encoding='utf-8') as f:
+            lines = f.readlines()
+        for lib in ('-ldl', '-lm'):
+            for line in lines:
+                if lib not in line:
+                    continue
+                # Assert that
+                self.assertEqual(len(line.split(lib)), 2, msg=(lib, line))
+
 
 def should_run_cross_arm_tests():
     return shutil.which('arm-linux-gnueabihf-gcc') and not platform.machine().lower().startswith('arm')

test cases/unit/55 dedup compiler libs/app/app.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <liba.h>
+#include <libb.h>
+
+int
+main(void)
+{
+	printf("start value = %d\n", liba_get());
+	liba_add(2);
+	libb_mul(5);
+	printf("end value = %d\n", liba_get());
+	return 0;
+}

test cases/unit/55 dedup compiler libs/app/meson.build

@@ -0,0 +1,2 @@
+executable('app', 'app.c',
+	dependencies: [get_variable('dep_liba'), get_variable('dep_libb')])

test cases/unit/55 dedup compiler libs/liba/liba.c

@@ -0,0 +1,18 @@
+#include "liba.h"
+
+static int val;
+
+void liba_add(int x)
+{
+	val += x;
+}
+
+void liba_sub(int x)
+{
+	val -= x;
+}
+
+int liba_get(void)
+{
+	return val;
+}

test cases/unit/55 dedup compiler libs/liba/liba.h

@@ -0,0 +1,8 @@
+#ifndef LIBA_H_
+#define LIBA_H_
+
+void liba_add(int x);
+void liba_sub(int x);
+int liba_get(void);
+
+#endif

test cases/unit/55 dedup compiler libs/liba/meson.build

@@ -0,0 +1,10 @@
+deps = [dependency('threads'), cc.find_library('dl'), cc.find_library('m')]
+
+liba = library('a', 'liba.c',
+	dependencies: deps)
+
+liba_dep = declare_dependency(link_with: liba,
+	include_directories: include_directories('.'),
+	dependencies: deps)
+
+set_variable('dep_liba', liba_dep)

test cases/unit/55 dedup compiler libs/libb/libb.c

@@ -0,0 +1,7 @@
+#include <liba.h>
+#include "libb.h"
+
+void libb_mul(int x)
+{
+	liba_add(liba_get() * (x - 1));
+}

test cases/unit/55 dedup compiler libs/libb/libb.h

@@ -0,0 +1,6 @@
+#ifndef _LIBB_H_
+#define _LIBB_H_
+
+void libb_mul(int x);
+
+#endif

test cases/unit/55 dedup compiler libs/libb/meson.build

@@ -0,0 +1,9 @@
+libb = library('b', 'libb.c',
+	dependencies: liba_dep)
+
+libb_dep = declare_dependency(link_with: libb,
+	include_directories: include_directories('.'),
+	dependencies: liba_dep)
+
+set_variable('dep_libb', libb_dep)
+

test cases/unit/55 dedup compiler libs/meson.build

@@ -0,0 +1,7 @@
+project('temp', 'C')
+
+cc = meson.get_compiler('c')
+
+subdir('liba')
+subdir('libb')
+subdir('app')