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From 864ecde569ce9fad636abe1135de33fdc94e6981 Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Thu, 5 Sep 2024 19:49:07 -0400
Subject: [PATCH 1/1] src/vecteur.cc: skip undefined behavior with a bounds
check
---
src/vecteur.cc | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/src/vecteur.cc b/src/vecteur.cc
index de10197..119d454 100644
--- a/src/vecteur.cc
+++ b/src/vecteur.cc
@@ -8490,6 +8490,17 @@ namespace giac {
}
else {
int C=col+1;
+ // mjo: C can be equal to cmax here, which makes buffer[C]
+ // illegal. In that case, however, nothing will happen
+ // below:
+ //
+ // 1. C = cmax ==> C >= (cmax-4), so the "for" loop is skipped
+ // 2. After the "for" loop, C += ptr-&buffer[C] sets C to zero
+ // 3. Now C = cmax means that the second "for" loop is skipped
+ //
+ // As a result, we can comment out this whole thing when
+ // C = cmax to avoid a crash.
+ if (C < cmax) {
longlong * ptr= &buffer[C],*ptrend=&buffer[0]+cmax-4;
const int *ptrN=&Nline[C];
for (;ptr<ptrend;ptrN+=4,ptr+=4){
@@ -8502,6 +8513,7 @@ namespace giac {
for (;C<cmax;++C){
buffer[C] -= coeff*Nline[C];
}
+ }
}
}
// copy back buffer to N[l]
--
2.44.2
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