[cfe-dev] [RFC] warning about unparenthized macro replacement lists (CERT/MISRA compliance)

Thu Apr 9 04:57:17 PDT 2015

Hello!

I have written a simple compiler warning for unparenthised macro replacement lists. Such macros violates both MISRA and CERT rules.

A compiler warning is written when there is dangerous usage.

For example it writes a warning here:

    #define A  1+2
    int x = A * 2;  // <- warning

My intention was to make sure that code is compliant to this CERT rule:
https://www.securecoding.cert.org/confluence/display/c/PRE02-C.+Macro+replacement+lists+should+be+parenthesized

However there are some interesting false positives..

I've tested it on these projects so far:
a52dec_0.7.4 aalib_1.4p5 aaphoto_0.43.1 abcm2ps_7.8.9 abcmidi_20141016 abe_1.1 acct_6.5.5 ace-of-penguins_1.3 achilles_2 acovea_5.1.1 acpi_1.7 acpitool_0.5.1 acr_0.9.9 acr38_1.7.11 adjtimex_1.29 adns_1.5.0~rc1 adolc_2.5.2 adtool_1.3.3 aephea_12-248 aespipe_2.4c aft_5.098 agedu_9723 aggregate_1.6 aiksaurus_1.2.1+dev-0.12 ajaxterm_0.10 ale_0.9.0.3 algol68g_2.8 allegro4.2_4.2.2 alsa-lib_1.0.28 alsaplayer_0.99.81 ample_0.5.7 amule-emc_0.5.2 anthy_9100h antlr_2.7.7 anubis_4.1.1+dfsg1 anyremote_6.4 anyremote2html_1.4 aolserver4_4.5.1 apache-mod-auth-ntlm-winbind_0.0.0.lorikeet+svn+801 apcupsd_3.14.8 aplus-fsf_4.22.1 apparix_07-261 apr_1.5.1 aprsd_2.2.5-13 aprsdigi_3.5.1 apsfilter_7.2.6 aptitude-robot_1.3.4 arc-gui-clients_0.4.6 archmbox_4.10.0 argtable2_9 aria2_1.18.8 arpack++_2.3 ascii2binary_2.14 asciidoc_8.6.9
babl_0.1.12 backintime_1.0.36 backupninja_1.0.1 bar_1.11.1 barcode_0.98+debian bash_4.3 bash-completion_2.1 bashdb_4.2.0.8 bbe_0.2.2 bc_1.06.95 bcpp_0.0.20050725 bdfresize_1.5 beecrypt_4.2.1 bfbtester_2.0.1 bibclean_2.11.4 biblememorizer_0.6.4 bibutils_5.4 biff_0.17.pre20000412 binfmtc_0.17 binutils_2.25 binutils-h8300-hms_2.16.1 bison_3.0.2.dfsg bison++_1.21.11 bld_0.3.4.1 blitz++_0.9 blktool_4 blm_0.9.3 bluez-hcidump_2.4 bmake_20140620 bmf_0.9.4 bml_0.6.1 boa_0.94.14rc21 bodr_9 boolstuff_0.1.14 bopm_3.1.3 bottlerocket_0.05b3 bristol_0.60.5 brltty_5.2~20141018 bsd-finger_0.17
m17n-docs_1.6.2 m17n-lib_1.6.4 m4_1.4.17 macchanger_1.7.0 mach_0.9.1 madlib_1.3.0 magic_7.5.241 magicfilter_1.2 magicrescue_1.1.9 mailfilter_0.8.3 mailtextbody_0.1.3 mailutils_2.99.98 makebootfat_1.4 makedepf90_2.8.8 makepp_2.0.98.5 maloc_0.2 maq_0.7.1 maradns_2.0.09 marisa_0.2.4 matanza_0.13+ds1 matchbox-themes-extra_0.3 maude_2.6 mauve_20140821 mboxgrep_0.7.9 mbr_1.1.11 mbuffer_20140310 mcl_14-137 mcpp_2.7.2 md5deep_4.3 mdds_0.5.4 mdf2iso_0.3.1 mecab_0.996 medicalterms_20110608 medusa_2.1.1 mell_1.0.0 mergelog_4.5.1 meschach_1.2b metastudent-data_1.0.1 metastudent-data-2_1.0.0 mew_6.6 mew-beta_7.0.50~6.6+0.20140902 mhash_0.9.9.9 mig_1.4 mimetic_0.9.8 min12xxw_0.0.9 mined_2000.15.4 minicom_2.7 minidjvu_0.8.svn.2010.05.06+dfsg minisapserver_0.3.6 miredo_1.2.6 miscfiles_1.5+dfsg missidentify_1.0 mkcue_1 mkelfimage_2.7 mlmmj_1.2.18.1 mlocate_0.26 mlt_0.9.6 mm_1.4.2 mm-common_0.9.7 mmdb_1.25.5 mmorph_2.3.4.2 moap_0.2.7 mobile-broadband-provider-info_20140317 mod-wsgi_4.3.0 module-init-tools_3.12 mona_1.4-15 monitoring-plugins_2.1.1
oath-toolkit_2.4.1 ocaml_4.02.1 ocl-icd_2.2.3 ocrad_0.24 octave-benchmark_1.1.1 octave-bioinfo_0.1.2 octave-combinatorics_1.0.9 octave-fixed_0.7.10 octave-ga_0.9.7 octave-ident_1.0.7 octave-informationtheory_0.1.8 octave-integration_1.0.7 octave-irsa_1.0.7 octave-mapping_1.0.7 octave-missing-functions_1.0.2 octave-multicore_0.2.15 octave-nlwing2_1.1.1 octave-outliers_0.13.9 octave-pdb_1.0.7 octave-physicalconstants_0.1.7 octave-secs2d_0.0.8 octave-simp_1.1.0 octave-struct_1.0.7 octave-symband_1.0.10 octave-time_1.0.9 octave-xraylib_1.0.8 octave-zenity_0.5.7 ocurl_0.5.3 ode_0.11.1 odyssey_0.4 oggvideotools_0.8a ogmtools_1.5 oidentd_2.0.8 omnievents_2.6.2 omniorb-dfsg_4.2.0 onak_0.4.5 onioncat_0.2.2+svn559 op_1.32 opari2_1.0.7+dfsg opencore-amr_0.1.3 opendchub_0.8.2 openfst_1.3.3 openh323_1.18.0.dfsg openload_0.1.2 openmama_2.2.2.1 openmpi_1.6.5 openmsx_0.8.2 openntpd_5.7p3 openocd_0.8.0 openresolv_3.5.2 openslp-dfsg_1.2.1

I have looked at some of the warnings....

There was warnings in abcm2ps_7.8.9. Example code:

    #define CM        * 28.35 /* factor to transform cm to pt */
    ...
    f->topmargin = 1.0 CM;
    ...

=> I believe the macro usage is intentional here. So it's likely a FP from the user perspective.

There was warnings in bc_1.06.95. There was code generated by flex like:

    #define BEGIN (yy_start) = 1 + 2 *
    ..
    BEGIN(slcomment);

=> imho stylistically this is code from hell but it's autogenerated. I guess users have to disable various warnings for autogenerated code?

In binutils there was such code:

    #define ILF_DATA_SIZE      + SIZEOF_ILF_SYMS + ...
    ...
    ptr = (bfd_byte *) bfd_zmalloc ((bfd_size_type) ILF_DATA_SIZE);
    vars.bim->buffer = ptr;
    vars.bim->size   = ILF_DATA_SIZE;

=> It would not hurt to add parentheses to the macro. For information, bfd_size_type is a type.

In brighton there was this code:

    #define K6W 1000 / 43
    ..
    {"", 2, 2 * K6W, KIH, K6W, KIL, 0, 1, 0,

=> hmm.. might be intended. If parentheses are used there is more truncation.

About abcm2ps_7.8.9 and brighton. The warnings are technically correct - the code violates MISRA/CERT rules. A user who wants his code to be compliant to the CERT rule would want to have these warnings. But I also understand that in these projects these warnings would be seen as FP. Do you think these are FP I should fix?

Technical question:
My checker has false negatives when the dangerous macro usage is inside a macro.
Currently my checker uses isMacroID(). It only tells me if an expression comes from some macro or not. I want to know if two expressions come from different macros.

Best regards,
Daniel Marjamäki

..................................................................................................................
Daniel Marjamäki Senior Engineer
Evidente ES East AB  Warfvinges väg 34  SE-112 51 Stockholm  Sweden

Mobile:                 +46 (0)709 12 42 62
E-mail:                 Daniel.Marjamaki at evidente.se

www.evidente.se
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