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Editorial Team
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Asked: 2026-06-17T08:26:21+00:00

I’d like to use -Wall and -Werror as flags for gcc in an autotools

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I’d like to use -Wall and -Werror as flags for gcc in an autotools project, but I don’t want to put them in my configure.ac.

As such, I tried using ./configure CFLAGS='-Wall -Werror', only to get an error from one of my AC_SEARCH_LIBS macro calls:

AC_SEARCH_LIBS([pow], [m], , AC_MSG_ERROR([Could not find standard math library.]))

Resulting error when running configure with the CFLAGS added:

configure: error: Could not find standard math library.

What am I doing wrong here? Configuration works fine without the CFLAGS variable set.

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1 Answer

  1. Editorial Team

    As you now know, elevating the compile warnings to errors confuses ./configure.

    What you can do is pass custom CFLAGS at make time:

    $ ./configure
$ make CFLAGS='-O2 -g -Wall -Wextra -Werror'

    The other option is William Pursell’s approach: add an option to ./configure to turn on -Werror if supported:

    (configure.ac)

    AC_ARG_ENABLE([werror],
              [AS_HELP_STRING([--enable-werror], [Use -Werror @<:@no@:>@])],
              [:],
              [enable_werror=no])
AM_CONDITIONAL([ENABLE_WERROR], [test "$enable_werror" = yes])

    (Makefile.am)

    if ENABLE_WERROR
AM_CFLAGS += -Werror
endif
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