Fix breakage of get_ps_display() in the PS_USE_NONE case.

tglsfdc · tglsfdc · commit 0fb6954aa501 · 2022-03-27T12:57:46.000-04:00
Commit 8c6d30f caused this function to fail to set *displen in the PS_USE_NONE code path. If the variable's previous value had been negative, that'd lead to a memory clobber at some call sites. We'd managed not to notice due to very thin test coverage of such configurations, but this appears to explain buildfarm member lorikeet's recent struggles. Credit to Andrew Dunstan for spotting the problem. Back-patch to v13 where the bug was introduced. Discussion: https://postgr.es/m/136102.1648320427@sss.pgh.pa.us
diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
@@ -443,6 +443,7 @@ get_ps_display(int *displen)
 
 	return ps_buffer + ps_buffer_fixed_size;
 #else
+	*displen = 0;
 	return "";
 #endif
 }

Original file line number	Diff line number	Diff line change
`@@ -443,6 +443,7 @@ get_ps_display(int *displen)`
`443`	`443`
`444`	`444`	`return ps_buffer + ps_buffer_fixed_size;`
`445`	`445`	`#else`
	`446`	`+ *displen = 0;`
`446`	`447`	`return "";`
`447`	`448`	`#endif`
`448`	`449`	`}`