[ft-devel] ftjam segfault building with GCC 4.2

[Ryan Hill]

Building ftjam with GCC 4.2 using -O2 optimizations fails with a
segfault in jam0.  This is caused by a violation of strict-aliasing
rules which GCC 4.2 assumes are followed with optimization levels of -O2
and above.  It can be worked around with -fno-strict-aliasing.  All jam
implementations appear to be affected, including Perforce jam, ftjam,
and Boost.Jam.


gcc -o jam0 -O2 -march=native -pipe -Wstrict-aliasing  builtins.c
command.c compile.c execnt.c execunix.c execvms.c expand.c filent.c
fileos2.c fileunix.c filevms.c glob.c hash.c hdrmacro.c headers.c jam.c
jambase.c jamgram.c lists.c make.c make1.c newstr.c option.c parse.c
pathunix.c pathvms.c regexp.c rules.c scan.c search.c timestamp.c variable.c
execunix.c: In function 'execcmd':
execunix.c:235: warning: incompatible implicit declaration of built-in
function '_exit'
hdrmacro.c: In function 'macro_headers':
hdrmacro.c:110: warning: dereferencing type-punned pointer will break
strict-aliasing rules
hdrmacro.c: In function 'macro_header_get':
hdrmacro.c:133: warning: dereferencing type-punned pointer will break
strict-aliasing rules
newstr.c: In function 'newstr':
newstr.c:52: warning: dereferencing type-punned pointer will break
strict-aliasing rules
rules.c: In function 'bindrule':
rules.c:62: warning: dereferencing type-punned pointer will break
strict-aliasing rules
rules.c: In function 'bindtarget':
rules.c:89: warning: dereferencing type-punned pointer will break
strict-aliasing rules
timestamp.c: In function 'timestamp':
timestamp.c:90: warning: dereferencing type-punned pointer will break
strict-aliasing rules
timestamp.c:116: warning: dereferencing type-punned pointer will break
strict-aliasing rules
timestamp.c:141: warning: dereferencing type-punned pointer will break
strict-aliasing rules
timestamp.c: In function 'time_enter':
timestamp.c:187: warning: dereferencing type-punned pointer will break
strict-aliasing rules
variable.c: In function 'var_get':
variable.c:235: warning: dereferencing type-punned pointer will break
strict-aliasing rules
variable.c: In function 'var_enter':
variable.c:327: warning: dereferencing type-punned pointer will break
strict-aliasing rules
chmod a+w jambase.c
./jam0
make: *** [all] Segmentation fault


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