-CFLAGS="$CFLAGS -W"
-
-warn_CFLAGS="-std=c89 -pedantic -Wall -Wextra -Wcast-align -Wnested-externs -Wshadow -Wstrict-prototypes -Wno-unused-function -Wno-long-long -Wno-overlength-strings"
-saved_CFLAGS="$CFLAGS"
-CFLAGS="$CFLAGS $warn_CFLAGS"
-AC_MSG_CHECKING([if ${CC} supports ${warn_CFLAGS}])
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
- [ AC_MSG_RESULT([yes]) ],
- [ AC_MSG_RESULT([no])
- CFLAGS="$saved_CFLAGS"
- ])
-
-saved_CFLAGS="$CFLAGS"
-CFLAGS="$CFLAGS -fvisibility=hidden"
-AC_MSG_CHECKING([if ${CC} supports -fvisibility=hidden])
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
- [ AC_MSG_RESULT([yes]) ],
- [ AC_MSG_RESULT([no])
- CFLAGS="$saved_CFLAGS"
- ])
+# Try if some desirable compiler flags are supported and append them to SECP_CFLAGS.
+#
+# These are our own flags, so we append them to our own SECP_CFLAGS variable (instead of CFLAGS) as
+# recommended in the automake manual (Section "Flag Variables Ordering"). CFLAGS belongs to the user
+# and we are not supposed to touch it. In the Makefile, we will need to ensure that SECP_CFLAGS
+# is prepended to CFLAGS when invoking the compiler so that the user always has the last word (flag).
+#
+# Another advantage of not touching CFLAGS is that the contents of CFLAGS will be picked up by
+# libtool for compiling helper executables. For example, when compiling for Windows, libtool will
+# generate entire wrapper executables (instead of simple wrapper scripts as on Unix) to ensure
+# proper operation of uninstalled programs linked by libtool against the uninstalled shared library.
+# These executables are compiled from C source file for which our flags may not be appropriate,
+# e.g., -std=c89 flag has lead to undesirable warnings in the past.
+#
+# TODO We should analogously not touch CPPFLAGS and LDFLAGS but currently there are no issues.
+AC_DEFUN([SECP_TRY_APPEND_DEFAULT_CFLAGS], [
+ # Try to append -Werror=unknown-warning-option to CFLAGS temporarily. Otherwise clang will
+ # not error out if it gets unknown warning flags and the checks here will always succeed
+ # no matter if clang knows the flag or not.
+ SECP_TRY_APPEND_DEFAULT_CFLAGS_saved_CFLAGS="$CFLAGS"
+ SECP_TRY_APPEND_CFLAGS([-Werror=unknown-warning-option], CFLAGS)
+
+ SECP_TRY_APPEND_CFLAGS([-std=c89 -pedantic -Wno-long-long -Wnested-externs -Wshadow -Wstrict-prototypes -Wundef], $1) # GCC >= 3.0, -Wlong-long is implied by -pedantic.
+ SECP_TRY_APPEND_CFLAGS([-Wno-overlength-strings], $1) # GCC >= 4.2, -Woverlength-strings is implied by -pedantic.
+ SECP_TRY_APPEND_CFLAGS([-Wall], $1) # GCC >= 2.95 and probably many other compilers
+ SECP_TRY_APPEND_CFLAGS([-Wno-unused-function], $1) # GCC >= 3.0, -Wunused-function is implied by -Wall.
+ SECP_TRY_APPEND_CFLAGS([-Wextra], $1) # GCC >= 3.4, this is the newer name of -W, which we don't use because older GCCs will warn about unused functions.
+ SECP_TRY_APPEND_CFLAGS([-Wcast-align], $1) # GCC >= 2.95
+ SECP_TRY_APPEND_CFLAGS([-Wcast-align=strict], $1) # GCC >= 8.0
+ SECP_TRY_APPEND_CFLAGS([-Wconditional-uninitialized], $1) # Clang >= 3.0 only
+ SECP_TRY_APPEND_CFLAGS([-fvisibility=hidden], $1) # GCC >= 4.0
+
+ CFLAGS="$SECP_TRY_APPEND_DEFAULT_CFLAGS_saved_CFLAGS"
+])
+SECP_TRY_APPEND_DEFAULT_CFLAGS(SECP_CFLAGS)
+
+###
+### Define config arguments
+###
projects / secp256k1.git / blobdiff