[PATCH] Don't call unsafe functions from SIGSEGV/SIGBUS signal handler.

[Mark Wielaard]

GCC10 -fanalyzer notices that we try to call functions that are not
signal safe from our fatal signal handler:

bzip2.c: In function ‘mySIGSEGVorSIGBUScatcher’:
bzip2.c:819:7: warning: call to ‘fprintf’ from within signal handler
               [CWE-479] [-Wanalyzer-unsafe-call-within-signal-handler]

It also notices we then call showFileNames and cleanupAndFail which
also call possibly not signal safe functions.

Just write out the error message directly to STDERR and exit without
trying to clean up any files.
---
 bzip2.c | 40 ++++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/bzip2.c b/bzip2.c
index d95d280..d1f2fa8 100644
--- a/bzip2.c
+++ b/bzip2.c
@@ -815,10 +815,9 @@ void mySignalCatcher ( IntNative n )
 static 
 void mySIGSEGVorSIGBUScatcher ( IntNative n )
 {
+   const char *msg;
    if (opMode == OM_Z)
-      fprintf ( 
-      stderr,
-      "\n%s: Caught a SIGSEGV or SIGBUS whilst compressing.\n"
+      msg = ": Caught a SIGSEGV or SIGBUS whilst compressing.\n"
       "\n"
       "   Possible causes are (most likely first):\n"
       "   (1) This computer has unreliable memory or cache hardware\n"
@@ -834,12 +833,9 @@ void mySIGSEGVorSIGBUScatcher ( IntNative n )
       "   bug report should have.  If the manual is available on your\n"
       "   system, please try and read it before mailing me.  If you don't\n"
       "   have the manual or can't be bothered to read it, mail me anyway.\n"
-      "\n",
-      progName );
-      else
-      fprintf ( 
-      stderr,
-      "\n%s: Caught a SIGSEGV or SIGBUS whilst decompressing.\n"
+      "\n";
+   else
+      msg = ": Caught a SIGSEGV or SIGBUS whilst decompressing.\n"
       "\n"
       "   Possible causes are (most likely first):\n"
       "   (1) The compressed data is corrupted, and bzip2's usual checks\n"
@@ -857,13 +853,25 @@ void mySIGSEGVorSIGBUScatcher ( IntNative n )
       "   bug report should have.  If the manual is available on your\n"
       "   system, please try and read it before mailing me.  If you don't\n"
       "   have the manual or can't be bothered to read it, mail me anyway.\n"
-      "\n",
-      progName );
-
-   showFileNames();
-   if (opMode == OM_Z)
-      cleanUpAndFail( 3 ); else
-      { cadvise(); cleanUpAndFail( 2 ); }
+      "\n";
+   write ( STDERR_FILENO, "\n", 1 );
+   write ( STDERR_FILENO, progName, strlen ( progName ) );
+   write ( STDERR_FILENO, msg, strlen ( msg ) );
+
+   msg = "\tInput file = ";
+   write ( STDERR_FILENO, msg, strlen (msg) );
+   write ( STDERR_FILENO, inName, strlen (inName) );
+   write ( STDERR_FILENO, "\n", 1 );
+   msg = "\tOutput file = ";
+   write ( STDERR_FILENO, msg, strlen (msg) );
+   write ( STDERR_FILENO, outName, strlen (outName) );
+   write ( STDERR_FILENO, "\n", 1 );
+
+   /* Don't call cleanupAndFail. If we ended up here something went
+      terribly wrong. Trying to clean up might fail spectacularly. */
+
+   if (opMode == OM_Z) setExit(3); else setExit(2);
+   _exit(exitValue);
 }
 
 
-- 
2.18.4