libmicrohttpd2

commit 2a142eb70804f1edb7d4d777aacaf78b2239ea1c
parent a50d5c0b5381914b6ac8370e23a26292efb97d7d
Author: Evgeny Grin (Karlson2k) <k2k@drgrin.dev>
Date:   Tue, 31 Mar 2026 05:16:07 +0200

Implemented detection and use of LTO

Diffstat:
M
configure.ac
 | 
90
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------

1 file changed, 84 insertions(+), 6 deletions(-)
diff --git a/configure.ac b/configure.ac
@@ -82,9 +82,9 @@ AS_IF([test -z "$CC" && test -z "$CPP"], [
 AC_MSG_CHECKING([for build type])
 AC_ARG_ENABLE([build-type],
   [AS_HELP_STRING([[--enable-build-type=TYPE]],
-  [enable build TYPE, a set of configuration parameters; individual settings ]
-  [(asserts, sanitizers, compiler and linker flags) can be overridden by ]
-  [additional configure parameters (debug, debugger, trace, neutral, release, ]
+  [enable build TYPE, a set of configuration parameters; individual settings ]dnl
+  [(asserts, sanitizers, compiler and linker flags) can be overridden by ]dnl
+  [additional configure parameters (debug, debugger, trace, neutral, release, ]dnl
   [release-compact, release-hardened) [neutral]])],
   [], [enable_build_type=neutral])
 AS_IF([test "x${enable_build_type}" = "x"], [enable_build_type="neutral"])
@@ -95,8 +95,8 @@ AS_CASE([${enable_build_type}],
   [trace], [AC_MSG_RESULT([trace. Defaults: enable asserts, debug prints, debug information, compiler optimisation for debugging])],
   [debugger], [AC_MSG_RESULT([debugger. Defaults: enable asserts, debug information, no compiler optimisation, static lib])],
   [neutral], [AC_MSG_RESULT([neutral. Defaults: use only user-specified compiler and linker flags])],
-  [release], [AC_MSG_RESULT([release. Defaults: disable asserts, enable compiler optimisations])],
-  [release-compact], [AC_MSG_RESULT([release-compact. Defaults: disable asserts, enable compiler optimisations for size, enable compact code])],
+  [release], [AC_MSG_RESULT([release. Defaults: disable asserts, enable compiler optimisations, LTO])],
+  [release-compact], [AC_MSG_RESULT([release-compact. Defaults: disable asserts, enable compiler optimisations for size, enable compact code, LTO])],
   [release-hardened], [AC_MSG_RESULT([release-hardened. Defaults: disable asserts, enable compiler optimisations, enable linker and compiler hardening])],
   [AC_MSG_ERROR([[Unknown build type: ${enable_build_type}]])]
 )
@@ -349,7 +349,7 @@ MHD_CHECK_ADD_CC_CFLAG([-qlonglong], [CFLAGS_ac])
 # Set basic optimisation flags
 AS_VAR_IF([enable_build_type],["neutral"],[],
   [ # Any non-neutral build types
-    AC_CACHE_CHECK([whether workarounds for clang or clang-based compiler are required],
+    AC_CACHE_CHECK([whether $CC is clang or clang-based],
       [mhd_cv_cc_clang_based],
       [
         AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
@@ -685,6 +685,83 @@ MHD_CHECK_CC_CFLAG([-Wc++-compat],[CFLAGS_ac],
 CFLAGS="${CFLAGS_ac} ${user_CFLAGS}"
 # Additional flags are checked and added at the end of 'configure'
 
+AC_ARG_ENABLE([lto],[AS_HELP_STRING([[--enable-lto[=ARG]]],[add Link Time Optimisation compiler flags (yes, no, auto) [auto]])],
+  [
+    AS_CASE([${enableval}],
+      [yes|no|auto],[],
+      [AC_MSG_ERROR([invalid parameter --enable-lto=${enableval}])]
+    )
+  ],[enable_lto=auto]
+)
+
+AS_VAR_IF([enable_lto],["auto"],
+  [AS_CASE([${enable_build_type}],[release|release-compact],[],[enable_lto=no])]
+)
+
+AS_VAR_IF([enable_lto],["no"],[use_lto="no"],
+  [
+    CFLAGS="${CFLAGS_ac} ${user_CFLAGS}"
+    LDFLAGS="${LDFLAGS_ac} ${user_LDFLAGS}"
+    lto_CFLAGS=""
+    lto_LDFLAGS=""
+    use_lto=""
+    AC_CACHE_CHECK([whether $CC is clang or clang-based],
+      [mhd_cv_cc_clang_based],
+      [
+        AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+#if ! defined(__clang__) && ! defined(__llvm__)
+#error Compiler is not clang-based
+fail test here %%%@<:@-1@:>@
+#endif
+              ]]
+            )
+          ],
+          [mhd_cv_cc_clang_based="yes"],[mhd_cv_cc_clang_based="no"]
+        )
+      ]
+    )
+    AS_VAR_IF([mhd_cv_cc_clang_based],["yes"],
+      [MHD_CHECK_ADD_CC_LDFLAG([-fuse-ld=lld],[lto_LDFLAGS])]
+    )
+    LDFLAGS="${lto_LDFLAGS} ${LDFLAGS_ac} ${user_LDFLAGS}"
+    MHD_FIND_ADD_CC_CFLAG_IFELSE(
+      [
+        use_lto="yes"
+        MHD_PREPEND_FLAG_TO_VAR([lto_LDFLAGS],[$mhd_cc_found_flag])
+      ],[use_lto="no"],[lto_CFLAGS],
+      [-flto=auto],[-flto=full],[-flto]
+    )
+    LDFLAGS="${lto_LDFLAGS} ${LDFLAGS_ac} ${user_LDFLAGS}"
+    AS_VAR_IF([use_lto],["yes"],
+      [
+        MHD_CHECK_ADD_CC_CFLAG([-ffat-lto-objects],[lto_CFLAGS],
+          [],
+          [
+            test "X${enable_static}" = "Xyes" && test "X${enable_lto}" = "Xauto" && use_lto="no"
+          ]
+        )
+      ]
+    )
+    AS_VAR_IF([use_lto],["yes"],
+      [MHD_FIND_ADD_CC_CFLAG([lto_CFLAGS],[-flto-partition=one],[-flto-partition=none])]
+    )
+    AS_VAR_IF([use_lto],["yes"],
+      [
+        MHD_PREPEND_FLAG_TO_VAR([CFLAGS_ac],[${lto_CFLAGS}])
+        MHD_PREPEND_FLAG_TO_VAR([LDFLAGS_ac],[${lto_LDFLAGS}])
+      ],
+      [
+        AS_VAR_IF([enable_lto],["yes"],
+          [AC_MSG_ERROR([LTO cannot be enabled, but requested by --enable-lto])]
+        )
+      ]
+    )
+    LDFLAGS="${LDFLAGS_ac} ${user_LDFLAGS}"
+    CFLAGS="${CFLAGS_ac} ${user_CFLAGS}"
+  ]
+)
+
+
 # Check for headers that are ALWAYS required
 AC_CHECK_HEADERS_ONCE([stdio.h string.h stdint.h stdarg.h errno.h limits.h fcntl.h], [],
   [AC_MSG_ERROR([Compiling libmicrohttpd requires standard C and POSIX headers files])], [AC_INCLUDES_DEFAULT])
@@ -9503,6 +9580,7 @@ AC_MSG_NOTICE([[${PACKAGE_NAME} ${PACKAGE_VERSION} Configuration Summary:
 
   [ Code build options ]
   Compact code     : ${enable_compact_code} (${compact_code_MSG})
+  LTO flags        : ${use_lto}
   Use thread names : ${enable_thread_names}
   Use debug asserts: ${use_asserts_MSG=no}
   Use sanitizers   : ${enabled_sanitizers:=no}