conan-io · franramirez688 · Jun 25, 2025 · Jun 24, 2025 · Jun 24, 2025 · Jun 25, 2025
diff --git a/conan/internal/default_settings.py b/conan/internal/default_settings.py
@@ -168,6 +168,7 @@
         # There is no ABI compatibility guarantee between versions
         version: [ANY]
         libcxx: [null, libstdc++, libstdc++11, libc++]
+        threads: [null, posix, wasm_workers]
         cppstd: [null, 98, gnu98, 11, gnu11, 14, gnu14, 17, gnu17, 20, gnu20, 23, gnu23, 26, gnu26]
         cstd: [null, 99, gnu99, 11, gnu11, 17, gnu17, 23, gnu23]
 

diff --git a/conan/tools/build/flags.py b/conan/tools/build/flags.py
@@ -195,6 +195,18 @@ def build_type_flags(conanfile):
             return flags
     return []
 
+def threads_flags(conanfile):
+    """
+    returns flags specific to the threading model used by the compiler
+    """
+    compiler = conanfile.settings.get_safe("compiler")
+    threads = conanfile.settings.get_safe("compiler.threads")
+    if compiler == "emcc":
+        if threads == "posix":
+            return ["-pthread"]
+        elif threads == "wasm_workers":
+            return ["-sWASM_WORKERS=1"]
+    return []
 
 def llvm_clang_front(conanfile):
     # Only Windows clang with MSVC backend (LLVM/Clang, not MSYS2 clang)

diff --git a/conan/tools/cmake/toolchain/blocks.py b/conan/tools/cmake/toolchain/blocks.py
@@ -10,7 +10,7 @@
 from conan.tools.android.utils import android_abi
 from conan.tools.apple.apple import is_apple_os, to_apple_arch
 from conan.tools.build import build_jobs
-from conan.tools.build.flags import architecture_flag, architecture_link_flag, libcxx_flags
+from conan.tools.build.flags import architecture_flag, architecture_link_flag, libcxx_flags, threads_flags
 from conan.tools.build.cross_building import cross_building
 from conan.tools.cmake.toolchain import CONAN_TOOLCHAIN_FILENAME
 from conan.tools.cmake.utils import is_multi_configuration
@@ -237,8 +237,8 @@ def context(self):
 
 class ArchitectureBlock(Block):
     template = textwrap.dedent("""\
-        # Define C++ flags, C flags and linker flags from 'settings.arch'
         {% if arch_flag %}
+        # Define C++ flags, C flags and linker flags from 'settings.arch'
         message(STATUS "Conan toolchain: Defining architecture flag: {{ arch_flag }}")
         string(APPEND CONAN_CXX_FLAGS " {{ arch_flag }}")
         string(APPEND CONAN_C_FLAGS " {{ arch_flag }}")
@@ -250,15 +250,23 @@ class ArchitectureBlock(Block):
         string(APPEND CONAN_SHARED_LINKER_FLAGS " {{ arch_link_flag }}")
         string(APPEND CONAN_EXE_LINKER_FLAGS " {{ arch_link_flag }}")
         {% endif %}
+        {% if thread_flags_list %}
+        # Define C++ flags, C flags and linker flags from 'compiler.threads'
+        message(STATUS "Conan toolchain: Defining thread flags: {{ thread_flags_list }}")
+        string(APPEND CONAN_CXX_FLAGS " {{ thread_flags_list }}")
+        string(APPEND CONAN_C_FLAGS " {{ thread_flags_list }}")
+        string(APPEND CONAN_SHARED_LINKER_FLAGS " {{ thread_flags_list }}")
+        string(APPEND CONAN_EXE_LINKER_FLAGS " {{ thread_flags_list }}")
+        {% endif %}
         """)
 
     def context(self):
         arch_flag = architecture_flag(self._conanfile)
         arch_link_flag = architecture_link_flag(self._conanfile)
-        if not arch_flag and not arch_link_flag:
+        thread_flags_list = " ".join(threads_flags(self._conanfile))
+        if not arch_flag and not arch_link_flag and not thread_flags_list:
             return
-        return {"arch_flag": arch_flag, "arch_link_flag": arch_link_flag}
-
+        return {"arch_flag": arch_flag, "arch_link_flag": arch_link_flag, "thread_flags_list": thread_flags_list}
 
 class LinkerScriptsBlock(Block):
     template = textwrap.dedent("""\

diff --git a/conan/tools/gnu/autotoolstoolchain.py b/conan/tools/gnu/autotoolstoolchain.py
@@ -7,7 +7,7 @@
 from conan.tools.build import cmd_args_to_string, save_toolchain_args
 from conan.tools.build.cross_building import cross_building
 from conan.tools.build.flags import architecture_flag, architecture_link_flag, build_type_flags, cppstd_flag, \
-    build_type_link_flags, libcxx_flags, cstd_flag, llvm_clang_front
+    build_type_link_flags, libcxx_flags, cstd_flag, llvm_clang_front, threads_flags
 from conan.tools.env import Environment, VirtualBuildEnv
 from conan.tools.gnu.get_gnu_triplet import _get_gnu_triplet
 from conan.tools.microsoft import VCVars, msvc_runtime_flag, unix_path, check_min_vs, is_msvc
@@ -53,6 +53,7 @@ def __init__(self, conanfile, namespace=None, prefix="/"):
         self.cstd = cstd_flag(self._conanfile)
         self.arch_flag = architecture_flag(self._conanfile)
         self.arch_ld_flag = architecture_link_flag(self._conanfile)
+        self.threads_flags = threads_flags(self._conanfile)
         self.libcxx, self.gcc_cxx11_abi = libcxx_flags(self._conanfile)
         self.fpic = self._conanfile.options.get_safe("fPIC")
         self.msvc_runtime_flag = self._get_msvc_runtime_flag()
@@ -203,7 +204,7 @@ def _filter_list_empty_fields(v):
     def cxxflags(self):
         fpic = "-fPIC" if self.fpic else None
         ret = [self.libcxx, self.cppstd, self.arch_flag, fpic, self.msvc_runtime_flag,
-               self.sysroot_flag]
+               self.sysroot_flag] + self.threads_flags
         apple_flags = [self.apple_isysroot_flag, self.apple_arch_flag, self.apple_min_version_flag]
         apple_flags += self.apple_extra_flags
         conf_flags = self._conanfile.conf.get("tools.build:cxxflags", default=[], check_type=list)
@@ -214,7 +215,7 @@ def cxxflags(self):
     @property
     def cflags(self):
         fpic = "-fPIC" if self.fpic else None
-        ret = [self.cstd, self.arch_flag, fpic, self.msvc_runtime_flag, self.sysroot_flag]
+        ret = [self.cstd, self.arch_flag, fpic, self.msvc_runtime_flag, self.sysroot_flag] + self.threads_flags
         apple_flags = [self.apple_isysroot_flag, self.apple_arch_flag, self.apple_min_version_flag]
         apple_flags += self.apple_extra_flags
         conf_flags = self._conanfile.conf.get("tools.build:cflags", default=[], check_type=list)
@@ -224,7 +225,7 @@ def cflags(self):
 
     @property
     def ldflags(self):
-        ret = [self.arch_flag, self.sysroot_flag, self.arch_ld_flag]
+        ret = [self.arch_flag, self.sysroot_flag, self.arch_ld_flag] + self.threads_flags
         apple_flags = [self.apple_isysroot_flag, self.apple_arch_flag, self.apple_min_version_flag]
         apple_flags += self.apple_extra_flags
         conf_flags = self._conanfile.conf.get("tools.build:sharedlinkflags", default=[],

diff --git a/conan/tools/gnu/gnutoolchain.py b/conan/tools/gnu/gnutoolchain.py
@@ -7,7 +7,7 @@
 from conan.tools.build.cross_building import cross_building
 from conan.tools.build.flags import architecture_flag, architecture_link_flag, build_type_flags, cppstd_flag, \
     build_type_link_flags, \
-    libcxx_flags, llvm_clang_front
+    libcxx_flags, llvm_clang_front, threads_flags
 from conan.tools.env import Environment, VirtualBuildEnv
 from conan.tools.gnu.get_gnu_triplet import _get_gnu_triplet
 from conan.tools.microsoft import VCVars, msvc_runtime_flag, unix_path, check_min_vs, is_msvc
@@ -58,6 +58,7 @@ def __init__(self, conanfile, namespace=None, prefix="/"):
         self.cppstd = cppstd_flag(self._conanfile)
         self.arch_flag = architecture_flag(self._conanfile)
         self.arch_ld_flag = architecture_link_flag(self._conanfile)
+        self.threads_flags = threads_flags(self._conanfile)
         self.libcxx, self.gcc_cxx11_abi = libcxx_flags(self._conanfile)
         self.fpic = self._conanfile.options.get_safe("fPIC")
         self.msvc_runtime_flag = self._get_msvc_runtime_flag()
@@ -268,7 +269,7 @@ def _dict_to_list(flags):
     def cxxflags(self):
         fpic = "-fPIC" if self.fpic else None
         ret = [self.libcxx, self.cppstd, self.arch_flag, fpic, self.msvc_runtime_flag,
-               self.sysroot_flag]
+               self.sysroot_flag] + self.threads_flags
         apple_flags = [self.apple_isysroot_flag, self.apple_arch_flag, self.apple_min_version_flag]
         apple_flags += self.apple_extra_flags
         conf_flags = self._conanfile.conf.get("tools.build:cxxflags", default=[], check_type=list)
@@ -279,7 +280,7 @@ def cxxflags(self):
     @property
     def cflags(self):
         fpic = "-fPIC" if self.fpic else None
-        ret = [self.arch_flag, fpic, self.msvc_runtime_flag, self.sysroot_flag]
+        ret = [self.arch_flag, fpic, self.msvc_runtime_flag, self.sysroot_flag] + self.threads_flags
         apple_flags = [self.apple_isysroot_flag, self.apple_arch_flag, self.apple_min_version_flag]
         apple_flags += self.apple_extra_flags
         conf_flags = self._conanfile.conf.get("tools.build:cflags", default=[], check_type=list)
@@ -289,7 +290,7 @@ def cflags(self):
 
     @property
     def ldflags(self):
-        ret = [self.arch_flag, self.sysroot_flag, self.arch_ld_flag]
+        ret = [self.arch_flag, self.sysroot_flag, self.arch_ld_flag] + self.threads_flags
         apple_flags = [self.apple_isysroot_flag, self.apple_arch_flag, self.apple_min_version_flag]
         apple_flags += self.apple_extra_flags
         conf_flags = self._conanfile.conf.get("tools.build:sharedlinkflags", default=[],

diff --git a/conan/tools/meson/toolchain.py b/conan/tools/meson/toolchain.py
@@ -9,7 +9,7 @@
 from conan.tools.apple.apple import is_apple_os, apple_min_version_flag, \
     resolve_apple_flags, apple_extra_flags
 from conan.tools.build.cross_building import cross_building
-from conan.tools.build.flags import architecture_link_flag, libcxx_flags, architecture_flag
+from conan.tools.build.flags import architecture_link_flag, libcxx_flags, architecture_flag, threads_flags
 from conan.tools.env import VirtualBuildEnv
 from conan.tools.meson.helpers import *
 from conan.tools.meson.helpers import get_apple_subsystem
@@ -218,6 +218,8 @@ def __init__(self, conanfile, backend=None, native=False):
         self.arch_flag = architecture_flag(self._conanfile)  # https://github.com/conan-io/conan/issues/17624
         #: Architecture link flag deduced by Conan and added to ``c_link_args`` and ``cpp_link_args``
         self.arch_link_flag = architecture_link_flag(self._conanfile)
+        #: Threads flags deduced by Conan and added to ``c_args``, ``cpp_args``, ``c_link_args`` and ``cpp_link_args``
+        self.threads_flags = threads_flags(self._conanfile)
         #: Dict-like object that defines Meson ``properties`` with ``key=value`` format
         self.properties = {}
         #: Dict-like object that defines Meson ``project options`` with ``key=value`` format
@@ -453,14 +455,14 @@ def _get_extra_flags(self):
         linker_script_flags = ['-T"' + linker_script + '"' for linker_script in linker_scripts]
         defines = self._conanfile_conf.get("tools.build:defines", default=[], check_type=list)
         sys_root = [f"--sysroot={self._sys_root}"] if self._sys_root else [""]
-        ld = sharedlinkflags + exelinkflags + linker_script_flags + sys_root + self.extra_ldflags
+        ld = sharedlinkflags + exelinkflags + linker_script_flags + sys_root + self.extra_ldflags + self.threads_flags
         # Apple extra flags from confs (visibilty, bitcode, arc)
         cxxflags += self.apple_extra_flags
         cflags += self.apple_extra_flags
         ld += self.apple_extra_flags
         return {
-            "cxxflags": [self.arch_flag] + cxxflags + sys_root + self.extra_cxxflags,
-            "cflags": [self.arch_flag] + cflags + sys_root + self.extra_cflags,
+            "cxxflags": [self.arch_flag] + cxxflags + sys_root + self.extra_cxxflags + self.threads_flags,
+            "cflags": [self.arch_flag] + cflags + sys_root + self.extra_cflags + self.threads_flags,
             "ldflags": [self.arch_flag] + [self.arch_link_flag] + ld,
             "defines": [f"-D{d}" for d in (defines + self.extra_defines)]
         }

diff --git a/conan/tools/premake/toolchain.py b/conan/tools/premake/toolchain.py
@@ -1,4 +1,4 @@
-from conan.tools.build.flags import architecture_flag, architecture_link_flag, libcxx_flags
+from conan.tools.build.flags import architecture_flag, architecture_link_flag, libcxx_flags, threads_flags
 import os
 import textwrap
 from pathlib import Path
@@ -16,19 +16,19 @@ def _generate_flags(self, conanfile):
     template = textwrap.dedent(
         """\
         {% if extra_cflags %}
-        -- C flags retrieved from CFLAGS environment, conan.conf(tools.build:cflags) and extra_cflags
+        -- C flags retrieved from CFLAGS environment, conan.conf(tools.build:cflags), extra_cflags and compiler settings
         filter { files { "**.c" } }
             buildoptions { {{ extra_cflags }} }
         filter {}
         {% endif %}
         {% if extra_cxxflags %}
-        -- CXX flags retrieved from CXXFLAGS environment, conan.conf(tools.build:cxxflags) and extra_cxxflags
+        -- CXX flags retrieved from CXXFLAGS environment, conan.conf(tools.build:cxxflags), extra_cxxflags and compiler settings
         filter { files { "**.cpp", "**.cxx", "**.cc" } }
             buildoptions { {{ extra_cxxflags }} }
         filter {}
         {% endif %}
         {% if extra_ldflags %}
-        -- Link flags retrieved from LDFLAGS environment, conan.conf(tools.build:sharedlinkflags), conan.conf(tools.build:exelinkflags) and extra_cxxflags
+        -- Link flags retrieved from LDFLAGS environment, conan.conf(tools.build:sharedlinkflags), conan.conf(tools.build:exelinkflags), extra_cxxflags and compiler settings
         linkoptions { {{ extra_ldflags }} }
         {% endif %}
         {% if extra_defines %}
@@ -47,27 +47,33 @@ def to_list(value):
     arch_flags = to_list(architecture_flag(self._conanfile))
     cxx_flags, libcxx_compile_definitions = libcxx_flags(self._conanfile)
     arch_link_flags = to_list(architecture_link_flag(self._conanfile))
+    thread_flags_list = threads_flags(self._conanfile)
 
     extra_defines = format_list(
         conanfile.conf.get("tools.build:defines", default=[], check_type=list)
         + self.extra_defines
         + to_list(libcxx_compile_definitions)
     )
     extra_c_flags = format_list(
-        conanfile.conf.get("tools.build:cflags", default=[], check_type=list) + self.extra_cflags + arch_flags
+        conanfile.conf.get("tools.build:cflags", default=[], check_type=list)
+        + self.extra_cflags
+        + arch_flags
+        + thread_flags_list
     )
     extra_cxx_flags = format_list(
         conanfile.conf.get("tools.build:cxxflags", default=[], check_type=list)
         + to_list(cxx_flags)
         + self.extra_cxxflags
         + arch_flags
+        + thread_flags_list
     )
     extra_ld_flags = format_list(
         conanfile.conf.get("tools.build:sharedlinkflags", default=[], check_type=list)
         + conanfile.conf.get("tools.build:exelinkflags", default=[], check_type=list)
         + self.extra_ldflags
         + arch_flags
         + arch_link_flags
+        + thread_flags_list
     )
 
     return (

diff --git a/test/integration/toolchains/cmake/test_cmaketoolchain.py b/test/integration/toolchains/cmake/test_cmaketoolchain.py
@@ -1772,3 +1772,35 @@ def test_cmake_presets_compiler():
     # https://github.com/microsoft/vscode-cmake-tools/blob/a1ceda25ea93fc0060324de15970a8baa69addf6/src/presets/preset.ts#L1095C23-L1095C35
     assert cache_variables["CMAKE_C_COMPILER"] == "cl"
     assert cache_variables["CMAKE_CXX_COMPILER"] == "cl.exe"
+
+@pytest.mark.parametrize(
+    "threads, flags",
+    [("posix", "-pthread"), ("wasm_workers", "-sWASM_WORKERS=1")],
+)
+def test_thread_flags(threads, flags):
+    client = TestClient()
+    profile = textwrap.dedent(f"""
+        [settings]
+        arch=wasm
+        build_type=Release
+        compiler=emcc
+        compiler.cppstd=17
+        compiler.threads={threads}
+        compiler.libcxx=libc++
+        compiler.version=4.0.10
+        os=Emscripten
+        """)
+    client.save(
+        {
+            "conanfile.py": GenConanfile("pkg", "1.0")
+            .with_settings("os", "arch", "compiler", "build_type")
+            .with_generator("CMakeToolchain"),
+            "profile": profile,
+        }
+    )
+    client.run("install . -pr=./profile")
+    toolchain = client.load("conan_toolchain.cmake")
+    assert f'string(APPEND CONAN_CXX_FLAGS " {flags}")' in toolchain
+    assert f'string(APPEND CONAN_C_FLAGS " {flags}")' in toolchain
+    assert f'string(APPEND CONAN_SHARED_LINKER_FLAGS " {flags}")' in toolchain
+    assert f'string(APPEND CONAN_EXE_LINKER_FLAGS " {flags}")' in toolchain
diff --git a/test/integration/toolchains/gnu/test_autotoolstoolchain.py b/test/integration/toolchains/gnu/test_autotoolstoolchain.py
@@ -1,6 +1,7 @@
 import os
 import platform
 import textwrap
+import pytest
 
 from conan.test.assets.genconanfile import GenConanfile
 from conan.test.utils.tools import TestClient
@@ -367,3 +368,40 @@ def test_conf_build_does_not_exist():
     tc = c.load("conanautotoolstoolchain.sh")
     assert 'export CC_FOR_BUILD="x86_64-linux-gnu-gcc"' in tc
     assert 'export CXX_FOR_BUILD="x86_64-linux-gnu-g++"' in tc
+
+@pytest.mark.parametrize(
+    "threads, flags",
+    [("posix", "-pthread"), ("wasm_workers", "-sWASM_WORKERS=1")],
+)
+def test_thread_flags(threads, flags):
+    os = platform.system()
+    client = TestClient()
+    profile = textwrap.dedent(f"""
+        [settings]
+        arch=wasm
+        build_type=Release
+        compiler=emcc
+        compiler.cppstd=17
+        compiler.threads={threads}
+        compiler.libcxx=libc++
+        compiler.version=4.0.10
+        os=Emscripten
+        """)
+    client.save(
+        {
+            "conanfile.py": GenConanfile("pkg", "1.0")
+            .with_settings("os", "arch", "compiler", "build_type")
+            .with_generator("AutotoolsToolchain"),
+            "profile": profile,
+        }
+    )
+    client.run("install . -pr=./profile")
+    toolchain = client.load("conanautotoolstoolchain{}".format('.bat' if os == "Windows" else '.sh'))
+    if os == "Windows":
+        assert f'set "CXXFLAGS=%CXXFLAGS% -stdlib=libc++ {flags}"' in toolchain
+        assert f'set "CFLAGS=%CFLAGS% {flags}"' in toolchain
+        assert f'set "LDFLAGS=%LDFLAGS% {flags}' in toolchain
+    else:
+        assert f'export CXXFLAGS="$CXXFLAGS -stdlib=libc++ {flags}"' in toolchain
+        assert f'export CFLAGS="$CFLAGS {flags}"' in toolchain
+        assert f'export LDFLAGS="$LDFLAGS {flags}"' in toolchain
diff --git a/test/integration/toolchains/gnu/test_gnutoolchain.py b/test/integration/toolchains/gnu/test_gnutoolchain.py
@@ -592,3 +592,43 @@ def build(self):
         "conanfile.py": consumer
     })
     client.run("create . -pr:h host -pr:b build")
+
+
+@pytest.mark.parametrize(
+    "threads, flags",
+    [("posix", "-pthread"), ("wasm_workers", "-sWASM_WORKERS=1")],
+)
+def test_thread_flags(threads, flags):
+    client = TestClient()
+    profile = textwrap.dedent(f"""
+        [settings]
+        arch=wasm
+        build_type=Release
+        compiler=emcc
+        compiler.cppstd=17
+        compiler.threads={threads}
+        compiler.libcxx=libc++
+        compiler.version=4.0.10
+        os=Emscripten
+        """)
+    client.save(
+        {
+            "conanfile.py": GenConanfile("pkg", "1.0")
+            .with_settings("os", "arch", "compiler", "build_type")
+            .with_generator("GnuToolchain"),
+            "profile": profile,
+        }
+    )
+    client.run("install . -pr=./profile")
+    os = platform.system()
+    toolchain = client.load(
+        "conangnutoolchain{}".format('.bat' if os == "Windows" else '.sh'))
+
+    if os == "Windows":
+        assert f'set "CXXFLAGS=%CXXFLAGS% -stdlib=libc++ {flags}"' in toolchain
+        assert f'set "CFLAGS=%CFLAGS% {flags}"' in toolchain
+        assert f'set "LDFLAGS=%LDFLAGS% {flags}' in toolchain
+    else:
+        assert f'export CXXFLAGS="$CXXFLAGS -stdlib=libc++ {flags}"' in toolchain
+        assert f'export CFLAGS="$CFLAGS {flags}"' in toolchain
+        assert f'export LDFLAGS="$LDFLAGS {flags}"' in toolchain