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Clang debug notes

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* etc/DEBUG: Don’t imply Clang works as well as GCC when
debugging Emacs.  Mention a coverage problem with Clang.
This commit is contained in:
Paul Eggert 2022-03-13 12:03:46 -07:00
parent ea3c147d2d
commit dd91aac508
1 changed files with 9 additions and 4 deletions
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13
etc/DEBUG
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@ -947,10 +947,10 @@ several kinds of low-level problems in C code, including:
* Passing invalid values to some builtin functions, e.g., __builtin_clz (0).
* Reaching __builtin_unreachable calls (in Emacs, 'eassume' failure).
To use UndefinedBehaviorSanitizer with GCC and similar compilers,
append '-fsanitize=undefined' to CFLAGS, either when running
'configure' or running 'make'. When supported, you can also specify
'bound-strict' and 'float-cast-overflow'. For example:
To use GCC's UndefinedBehaviorSanitizer, append '-fsanitize=undefined'
to CFLAGS, either when running 'configure' or running 'make'.
When supported, you can also specify 'bound-strict' and
'float-cast-overflow'. For example:
./configure \
CFLAGS='-O0 -g3 -fsanitize=undefined,bounds-strict,float-cast-overflow'
@ -958,6 +958,11 @@ append '-fsanitize=undefined' to CFLAGS, either when running
You may need to append '-static-libubsan' to CFLAGS if your version of
GCC is installed in an unusual location.
Clang's UB sanitizer can also be used, but has coverage problems.
You'll need '-fsanitize=undefined -fno-sanitize=pointer-overflow' to
suppress misguided warnings about adding zero to a null pointer,
although this also suppresses any valid pointer overflow warnings.
When using GDB to debug an executable with undefined-behavior
sanitization, the GDB command: